Chapter 1 : Periodic Table, Periodic Properties and Variations of Properties - Selina Solutions for Class 10 Chemistry ICSE

Chemistry is an important subject in ICSE Class 10, as the fundamentals studied now will also be helpful in the competitive exams like IIT-JEE and NEET. TopperLearning presents study materials for ICSE Class 10 Chemistry to help students to score well in the examination. All our study materials are created by subject experts and give basic insight on about how and what to prepare for the final exams.

Read  more
Page / Exercise

Chapter 1 - Periodic Table, Periodic Properties and Variations of Properties Excercise Intext 1

Question 1

(i) State modern periodic law.

(ii) Name the scientist who stated the law.

(iii) How many groups and periods does modern periodic table have?

Solution 1

(i) The modern periodic law states that "The properties of elements are the periodic functions of their atomic number."

(ii) Henry Moseley put forward the modern periodic law.

(iii) Modern Periodic table has 7 periods and 18 groups.

Question 2

What are horizontal rows and vertical columns in a periodic table known as?

Solution 2

The horizontal rows are known as periods and vertical columns in theperiodic table are known as groups.

Question 3

Periodicity is observed due to the similar.............

(number of valence electrons/ atomic number/ electronic configuration)

Solution 3

Periodicity is observed due to the similar electronic configuration.

Question 4

How does electronic configuration in atoms change

(i) In a period from left to right?

(ii) In a group top to bottom?

Solution 4

(i) Though the number of shells remain the same, number of valence electrons increases by one, as we move across any given period from left to right.

(ii) While going from top to bottom in a group, the number of shells increases successively i.e. one by one but the number of valence electrons remains the same.

Question 5

Name 2 elements in each case:

(i) Alkali metals

(ii) Alkaline earth metals

(iii) Halogens

(iv) Inert gas

(v) Transition metals

(vi) Lanthanides

(vii) Actinides

Solution 5

(i) Sodium and Potassium

(ii) Calcium and Magnesium

(iii) Chlorine and Bromine

(iv) Neon and Argon

(v) Iron and Cobalt

(vi) Cerium and Europium

(vii) Uranium and Neptunium

Question 6

Elements of group 1 and elements of group 17 both have valency1. Explain.

Solution 6

Valency is the combining capacity of the atom of an element. It is equal to the number of electrons an atom can donate or accept or share. It is just a number and does not have a positive or negative sign.

Group 1elements have 1 electron in their outermost orbital, while Group 7 elements have 7 electrons in their outermost orbital.

Valency depends on the number of electrons in the outermost shell (i.e. valence shell).

If the number of electrons present in the outermost shell is 1, then it can donate one electron while combining with other elements to obtain a stable electronic configuration.

If the number of electrons present in the outermost shell is 7, then its valency is again 1 (8 - 7 = 1) as it can accept 1 electron from the combining atom.

In a given period, the number of electrons in the valence (outermost) shell increases from left to right. But the valency increases only up to Group 14, where it becomes 4, and then it decreases, that is, it becomes 1 in Group 17.

 

 

Question 7

Correct the statements.

(i) Elements in the same period have equal valency.

(ii) Valency depends upon the number of shells in an atom.

(iii) Copper and zinc are representative elements.

(iv) Transition elements are placed at the extreme right of the periodic table.

Solution 7

(i) Elements in the same group have equal valency.

(ii) Valency depends upon the number of valence electrons in an atom.

(iii) Copper and zinc are transition elements.

(iv) Noble gases are placed at the extreme right of the periodic table.

Question 8

What do you understand by?

(i) Periodicity

(ii) Typical elements

(iii) Orbits

Solution 8

(i) The properties that reappear at regular intervals, or in which there is a gradual variation at regular intervals, are called periodic properties and the phenomenon is known as the periodicity of elements.

(ii) The third-period elements, Na, Mg, Al, Si, P and Cl summarize the properties of their respective groups and are called typical elements.

(iii) Elements revolve around the nucleus in certain definite circular paths called orbits or shells.

Question 9

Name 2 elements you would expect to show chemical reactions similar to calcium. What is the basis of your choice?

Solution 9

Beryllium and magnesium will show similar chemical reactions as calcium. Since these elements belong to same group 2 andalso have two electrons in their outermost shell like calcium.

Question 10

Name the (i) metals, (ii) metalloids and (iii) non-metals in the first twenty elements.

Solution 10
  1. Metals: Lithium, Beryllium, Sodium, Magnesium, Aluminium, Potassium, Calcium
  2. Metalloids: Boron, Silicon
  3. Non-metals: Hydrogen, Helium, Carbon, Nitrogen, Oxygen, Fluorine, Neon, Phosphorous, Sulphur, Chlorine, Argon 
Question 11

Fluorine, Chlorine and Bromine are put in one group on the basis of their similar properties.

  1. What are those similar properties?
  2. What is the common name of this group or family? 
Solution 11
 (i) Properties: Non-metallic, highest electronegativity in the respective periods, highest ionisation potentials in the respective periods, highest electron affinity in the respective periods

 (ii) Salt-forming; hence, the common name is halogens. 
Question 12

What is the main characteristic of the last element in each period of the Periodic Table? What is the general name of such elements?

Solution 12

The main characteristic of the last element in each period of the periodic table is they are inert or chemically unreactive.

The general name of such elements is 'Noble gases'.

Question 13

According to atomic structure, what determines which element will be the first and which will be the last in a period?

Solution 13

According to atomic structure, the number of valence electrons determines the first and the last element in a period.

Question 14

How does the number of :

i. Valence electrons and

ii. Valency vary on moving from left to right in the third period of the periodic table?

Solution 14

i. The valence electrons increase from 1 to 8 in the 3rd period of the periodic table.

ii. On moving from left to right, the valency increases from 1 to 4 and then decreases from 4 to 0.

Question 15

Name the type of elements, which have their

(i)Outermost shell complete

(ii)Outermost shell incomplete

(iii) Two outermost shells incomplete

(iv)One electron short of octet

(v) Two electrons in the outermost orbit.

Solution 15

(i) Noble gases

(ii) Representative elements

(iii) Transition elements

(iv) Halogens

(v) Alkaline Earth metals

Question 16

An element has 2 electrons in its N shell

(i) What is its atomic number?

(ii) State its position in periodic table

(iii) Is it metal or non-metal?

(iv) State the name assigned to this group.

Solution 16

(i) 30

(ii) It belongs to group 12 and fourth period.

(iii) It is a metal.

(iv) The name assigned to this group is IIB.

Question 17

Answer the following in respect of element 3216S.

(i)Give its electronic configuration.

(ii)To which group and period does it belong?

(iii)What is its valency?

(iv)Is it metal or non-metal?

(v)Is it a reducing agent or oxidizing agent?

(vi)Give its formula with chlorine.

Solution 17

(i) Electronic configuration of S: 2,8,6

(ii) 16th Group and 3rd Period.

(iii) Valency of S = 8 - 6 = 2

(iv) Sulphur is a non-metal.

(v) It is an oxidizing agent.

(vi) Formula with chlorine = SCl2

Chapter 1 - Periodic Table, Periodic Properties and Variations of Properties Excercise Intext 2

Question 1

What do you understand by atomic size? State its unit.

Solution 1

Atomic size is the distance between the centre of the nucleus of an atom and its outermost shell.

It's measured in Angstrom and Picometre.

Question 2

Give the trends in atomic size on moving

(i) Down the group

(ii) Across the period left to right.

Solution 2

(i) The atomic size of an atom increases when we go down a group from top to bottom.

(ii) It decreases as we move from left to right in a period.

Question 3

Arrange the elements of second and third period in increasing order of their atomic size.

Solution 3

Second Period: Fluorine < Neon < Oxygen < Nitrogen < Carbon < Boron < Beryllium < Lithium.

Third Period: Chlorine < Argon < Sulphur < Phosphorus < Silicon < Aluminum < Magnesium < Sodium.

Question 4

Why is the size of

(i) Neon greater than fluorine

(ii) Sodium is greater than magnesium.

Solution 4

(i) The size of Neon is bigger compared to fluorine because the outer shell of neon is complete(octet).As a result, the effect of nuclear pull over the valence shell electrons cannot be seen. Hence the size of Neon is greater than fluorine.

(ii) Since atomic number of magnesium is more than sodium but the numbers of shells are same, the nuclear pull is more in case of Mg atom. Hence its size is smaller than sodium.

Question 5

Which is greater in size

(i) An atom or a cation?

(ii) An atom or an anion?

(iii) Fe 2+ or Fe3+?

Solution 5

(i) An atom is always bigger than cation since cation is formed by the loss of electrons; hence protons are more than electrons in a cation. So the electrons are strongly attracted by the nucleus and are pulled inward.

(ii) An anion is bigger than an atom since it is formed by gain of electrons and so the number of electrons are more than protons. The effective positive charge in the nucleus is less, so less inward pull is experienced. Hence the size expands.

(iii) Fe 2+ is bigger than Fe3+ since Fe 2+ has more number of electrons than Fe3+ and hence the inner pull by nucleus is less strong on it as compared to the pull on Fe3+.

Question 6

Arrange :

  1. Be, Li, C, B, N, O, F (in increasing metallic character)
  2. Si, Na, Al, Mg, Cl, P, S (in decreasing non-metallic character) 
Solution 6
  1. In increasing metallic character: F < O < N < C < B < Be < Li
  2. In decreasing non-metallic character: Cl > S > P > Si > Al > Mg > Na 
Question 7

State the trends in chemical reactivity:

(i) Across the period left to right

(ii) Down the group

Solution 7

(i) Across a period, the chemical reactivity of elements first decreases and then increases.

(ii) Down the group, chemical reactivity increases as the tendency to lose electrons increases down the group.

Question 8

A metal M forms an oxide having the formula M2O3. It belongs to the third period. Write the atomic number and valency of the metal.

Solution 8

Given: The metal belongs to the third period; there are three shells.


The chemical formula of the compound suggests that the valency of the metal is +3.

That means the valence electrons are 3; hence, it belongs to the third group.


Thus, the element must have the electronic configuration 2, 8, 3.

That means the total number of electrons is 13.


Valency = 3, Atomic number = 13

Question 9

An element X belong to 3rd period and 17th group, state

(i) no of valence electrons in it.

(ii) name of the element.

(iii) name the family to which it belongs.

(iv) write the formula of the compound formed when it reacts with .

Solution 9

(i) The element from the 17th group has 7 electrons in its outermost shell.

(ii) The name of the element is chlorine.

(iii) Chlorine belongs to the halogen family.

(iv) The element has three electrons in its outermost shell which it can donate; hence, its valency is three. While the valency of chlorine is 1. Thus,   which is Aluminium can donate three electrons, and chlorine can accept 1 electron to get the stable electronic configuration. 

Therefore, the formula of the compound is AlCl3.

Question 10

The given table shows elements with same number of electrons in its valence shell.

Elements

A

B

C

m.p 

63.0

180.0

97.0

State :

(i) Whether these elements belong to same group or period.

(ii) Arrange them in order of increasing metallic character.

Solution 10

(i) Yes, these elements belong to the same group but are not from the same period.

(ii) We know that m.p. decreases on going down the group. Hence, from the above table, the elements can be ordered according to their period as follows:

Elements

B

C

A

m.p.

180.0

97.0

63.0

The metallic character increases as one moves down the group.

Hence, the order of the given elements with increasing metallic character is as follows:

B

Question 11

Which one of the following has the largest atomic radius?

 i. Sodium

 ii. Potassium

 iii. Magnesium

 iv. Aluminium 

Solution 11

Correct option: (ii) Potassium

Question 12

Which one has the largest size?

 i. Br

 ii. I

 iii. I-

 iv. Cl 

Solution 12

Correct option: (iii) I-

Question 13

The metals of group 2 from top to bottom are Be, Mg, Ca, Sr and Ba.

  1. Which one of these elements will form ions most readily and why?
  2. State the common feature in their electronic configuration. 
Solution 13

(i)  Barium will form ions most readily as the outermost valence electron which experiences the least force of attraction by positively charged nucleus can be given away readily to form cations.


(ii)All Group II elements have two valence electrons. 

Question 14

  

Solution 14

  

Protons = 19, Neutrons = 39 - 19 = 20

Electronic configuration = 1s22s22p63s23p64s1 

Position in the periodic table = Group 1, Period 4

  

Protons = 15, Neutrons = 31 - 15 =16

Electronic configuration = 1s2 2s2 2p6 3s2 3p3 

Position in the periodic table = Group 3, Period 3

Question 15

The electronic configuration of an element T is 2, 8, 8, 1.

  1. What is the group number of T?
  2. What is the period number of T?
  3. How many valence electrons are there in an atom of T?
  4. What is the valency of T?
  5. Is it a metal or a non-metal? 
Solution 15
  1. Group = 1
  2. Period = 4
  3. Valence electrons = 1
  4. Valency = 1
  5. Metal 
Question 16

The element barium has atomic number 56. Look up its position in the periodic table and answer the following questions:

(i) Is it a metal or a non-metal?

(ii) Is it more or less reactive than calcium?

(iii) What is its valency?

(iv) What will be the formula of its phosphate?

(v) Is it larger or smaller than caesium (Cs) in size?

Solution 16

(i) It belongs to group II and has 2 valence electrons, so it is a metal.

(ii) Barium is placed below calcium in the group. Since the reactivity increases below the group, barium is more reactive than calcium.

(iii) It needs to lose 2 valence electrons to complete its octet configuration, so its valency is 2.

(iv) The formula of its phosphate will be Ba3 (PO4)2.

(v) As we move from left to right in a period, the size decreases, so it will be smaller than caesium.

Question 17

In group I of the periodic table, three elements X,Y and Z have ionic radii 1.33  , 0.95   and 0.60  , respectively. Giving a reason, arrange them in the order of increasing atomic numbers in the group.

Solution 17

Sincethe size of the atom increases down the group, the ionic radii will also increase. Hence, the order of increasing atomic numbers in the group is Z < Y < X.

Question 18

Explain why are the following statements are not correct:

(i) All groups contain metal and non-metal.

(ii) Atoms of elements in the same group have same number of electron(s).

(iii) Non-metallic character decreases across a period with increase in atomic number.

(iv) Reactivity increases with atomic number in group as well as in a period.

 

Solution 18

(i) All groups do not contain both metals and non-metals. Group I and II contain only metals.

(ii) Atoms of elements in the same group have same number of valence electrons. They have same number of electrons present in their outermost shell.

(iii) The non-metallic character increases across a period with increase in atomic number. This is because across the period, the size of atom decreases and the valence shell electrons are held more tightly.

(iv) On moving from left to right in a period, the reactivity of elements first decreases and then increases, while in groups, chemical reactivity of metals increases going down the group whereas reactivity of non-metals is decreases down the group.

Question 19

Match the atomic number 19,15,8,4 and 2 with each of the following:

(i) A metal of valency one

(ii) A solid non-metal of period 3

(iii) A rare gas

(iv) A gaseous element with valency 2

(v) An element of group 2

Solution 19

(i) A metal of valency one = 19

(ii) A solid non-metal of period 3 = 15

(iii) A rare gas = 2

(iv) A gaseous element with valency 2 = 8

(v) An element of group 2 = 4

Question 20

Complete the following sentences choosing the correct word or words from those given in brackets at the end of each sentence:

  1. The properties of the elements are a periodic function of their _____ (atomic number, mass number, relative atomic mass).
  2. Moving across a _____ of the periodic table, the elements show increasing _____ character (group, period, metallic, non-metallic).
  3. The elements at the bottom of a group would be expected to show _____ metallic character than the element at the top (less, more).
  4. The similarities in the properties of a group of elements are because they have the same _____ (electronic configuration, number of outer electrons, atomic numbers). 
Solution 20

  (i)The properties of the elements are a periodic function of their atomic number.


 (ii)Moving across a period of the periodic table, the elements show increasing non-metallic character.


(iii)The elements at the bottom of a group would be expected to show more metallic character than the elements at the top.


(iv)The similarities in the properties of a group of elements are because they have the same number of outer electrons. 

Question 21

Give reasons for the following:

The size of a Cl- ion is greater than the size of a Cl atom.

Solution 21

An anion is formed by the gain of electrons. In the chloride ion, the number of electrons is more than the number of protons. The effective positive charge in the nucleus is less, so the less inward pull is experienced. Hence, the size expands.

  

Question 22

Give reasons for the following:

Argon atom is bigger than chlorine atom.

Solution 22

The inert gas argon is the next element after chlorine in the third period.

In a period, the size of an atom decreases from left to right due to an increase in nuclear charge with an increase in the atomic number. However, the size of the atoms of inert gases is bigger than the previous atom of halogen in the respective period. This is because the outer shell of inert gases is complete. They have the maximum number of electrons in their outermost orbit; thus, electronic repulsions are maximum. Hence, the size of the atom of an inert gas is bigger.

Question 23

Give reasons for the following:

Ionisation potential of the element increases across a period.

Solution 23

Ionisation potential of the element increases across a period because the atomic size decreases due to an increase in the nuclear charge, and thus, more energy is required to remove the electron(s).

Question 24

Inert gases do not form ion.

Solution 24

To attain stability, atoms need to complete their octet by sharing, losing or gaining electrons. In inert gases, the octet is complete, and they do not need to gain, lose or share electrons. Hence, inert gas elements do not form ions. 

Question 25

Name the element which has:

two shells, both of which are completely filled with electrons?

Solution 25

Neon (Atomic number = 10)

Electronic configuration = 1s22s22p6

Question 26

Name the element which has:

the electronic configuration 2, 8, 3?

Solution 26

Electronic configuration = 2, 8, 3

Hence, atomic number = 13

The element having atomic number 13 is Aluminium.

Question 27

Name the element which has:

a total of three shells with five electrons in its valence shell?

Solution 27

The element has a total of three shells; hence, the element belongs to the third period.

Five valence electrons indicate that the element belongs to the fifth group (VA).

Hence, the element is phosphorus.

Question 28

Name the element which has:

a total of four shells with two electrons in its valence shell.

Solution 28

The element has a total of four shells; hence, the element belongs to the fourth period.

Two valence electrons indicate that the element belongs to the second group (IIA).

Hence, the element is calcium.

Question 29

Name the element which has:

twice as many electrons in its second shell as in its first shell?

Solution 29

Twice as many electrons in its second shell as in its first shell indicates electronic configuration 1s22s2.

From the electronic configuration, the total number of electrons is 4.

We know that

Number of electrons = Number of protons = Atomic number

The element with atomic number 4 is beryllium.

Question 30

State the number of elements in Period 1, Period 2 and Period 3 of the periodic table. Name them.

Solution 30

Period 1:

Number of elements = 2

Hydrogen, helium

Period 2:

Number of elements = 8

Lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, neon

Period 3:

Number of elements = 8

Sodium, magnesium, aluminium, silicon, phosphorus, sulphur, chlorine, argon

Question 31

What is the common feature of the electronic configuration of the elements at the end of Period 2 and Period 3?

Solution 31

A common feature of the electronic configuration of the elements at the end of Period 2 and Period 3 is that the atoms have 8 electrons in their outermost shell.

Question 32

If an element is in Group 17, it is likely to be ______ [metallic/non-metallic] in character, while with one electron in its outermost energy level (shell), then it is likely to be _______ [metallic/non-metallic].

Solution 32

If an element is in Group 17, it is likely to be non-metallic in character, while with one electron in its outermost energy level (shell), then it is likely to be metallic.

Chapter 1 - Periodic Table, Periodic Properties and Variations of Properties Excercise Intext 3

Question 1

(a) Define the term 'ionization potential'.

(b) Represent it in the form of an equation. In which unit it is measured?

Solution 1

(a) The energy required to remove an electron from a neutral isolated gaseous atom amd convert it into a positively charged gaseous ion is called Ionization energy or ionization potential.

(b) M(g)+ I.E M+(g)+ e-

M can be any element

It is measured in electron volts per atom. It's S.I unit kJmol-1.

Question 2

Ionisation Potential values depend on

a. atomic size

b. nuclear pull. Explain.

Solution 2

Ionisation potential values depend on

a. Atomic size: The greater the atomic size, the lesser the force of attraction. Electrons of the outermost shell lie further away from the nucleus, so their removal is easier and the ionisation energy required is less.

b. Nuclear charge: The greater the nuclear charge, greater is the attraction for the electrons of the outermost shell. Therefore, the electrons in the outermost shell are more firmly held because of which greater energy is required to remove them.

Question 3

State the trends in ionization energy:

(a) across the period

(b) down the group

Solution 3

(a) Ionization energy increases as we move from left to right across a period as the atomic size decreases.

(b) Ionization energy decreases down a group as the atomic size increases.

Question 4

Name the elements with highest and lowest ionization energies in first three periods

Solution 4

Helium has the highest ionization energy of all the elements while Sodium has the lowest ionization energy in first three periods.

Question 5

Arrange the elements of second and third period in increasing order of ionization energy.

Solution 5

Second period: Lithium < Beryllium < Boron < Carbon < Nitrogen < Oxygen < Fluorine < Neon

 

Third Period:Sodium < Magnesium < Aluminum < Silicon < Phosphorus < Sulphur < Chlorine < Argon

Question 6

(a) Define the term electron affinity.

(b) Arrange the elements of second period in increasing order of electron affinity. Name the elements which do not follow the trend in this period.

Solution 6

(a) Electron affinity is the energy released when a neutral gaseous atom acquires an electron to form an anion.

(b) Second period: Lithium

Neon, Nitrogen and Beryllium do not follow the trend.

Question 7

Electron affinity values generally ----- across the period left to right and ------down the group top to bottom.

Solution 7

Electron affinity values generally increase across the period left to right and decrease down the group top to bottom.

Question 8

Define the term 'Electronegativity'. State its unit.

Solution 8

Electronegativity is the tendency of an atom in a molecule to attract the shared pair of electrons towards itself.

Electronegativity is a dimensionless property; hence, it has no unit.

Question 9

Among the elements given below, the element with least electronegativity is

(i) Lithium, (ii) Boron, (iii) Carbon, (iv) Fluorine

Solution 9

Correct option - (i).

The element with least electronegativity is lithium.

Question 10

Explain the following :

(a) Group 17 elements are strong non-metals, while group I elements are strong metals.

(b) Metallic character of elements decreases from left to right in a period while it increases in moving down a group.

(c) Halogens have a high electron affinity.

(d) The reducing power of element increases down in the group while decreases in a period.

(e) Size of atoms progressively becomes smaller when we move from sodium (Na) to chlorine (Cl) in the third period of the periodic Table.

Solution 10

(a) On moving across a period, nuclear pull increases because of the increase in atomic number, and thus, the atomic size decreases. Hence, elements cannot lose electrons easily. Hence, Group 17 elements are strong non-metals, while Group 1 elements are strong metals.


(b)  On moving across a period, nuclear pull increases because of the increase in atomic number, and thus, the atomic size decreases. Hence, elements cannot lose electrons easily. Hence, Group 17 elements are strong non-metals, while Group 1 elements are strong metals. Down a group, the atomic size increases and the nuclear charge also increases. The effect of an increased atomic size is greater as compared to the increased nuclear charge. Therefore, metallic nature increases as one moves down a group, i.e. they can lose electrons easily.


(c) The atomic size of halogens is very small. The smaller the atomic size, the greater the electron affinity, because the effective attractive force between the nucleus and the valence electrons is greater in smaller atoms, and so the electrons are held firmly.


(d) The reducing property depends on the ionisation potential and electron affinity of the elements. In a period, from left to right in a horizontal row of the periodic table, the atomic size decreases and the nuclear charge increases, so the electron affinity and ionisation energy both increase. Hence, the tendency to lose electrons decreases across the period from left to right and thus the reducing property also decreases across the period from left to right.  

The electron affinity and ionisation potential decrease along the group from top to bottom. Hence, the tendency to lose electrons increases, and thus, the reducing property also increases along the group from top to bottom. 


(e) In a period, the size of an atom decreases from left to right. This is because the nuclear charge, i.e. the atomic number increases from left to right in the same period, thereby bringing the outermost shell closer to the nucleus. Therefore, considering the third period given above, it has been found that sodium is the largest in size, while chlorine is the smallest. 

Question 11

Name the periodic property which relates tothe

(i) Amount of energy required to remove an electron from an isolated gaseous atom.

(ii) Character of element which loses one or more electrons when supplied with energy.

(iii) Tendency of an atom to attract the shared pair of electrons.

Solution 11

(i) Ionization energy

(ii) Metallic character

(iii) Electronegativity

Question 12

This question refers to the elements of the periodic table with atomic numbers from 3 to 18. Some of the elements are shown by letters, but the letters are not the usual symbols of the elements.

3 4 5 6 7 8 9 10

A B C D E F G H

11 12 13 14 15 16 17 18

I J K L M N O P

Which of these

  1. are the most electronegative element
  2. is a halogen
  3. is an alkali metal
  4. is an element with valency 4
  5. have least ionisation energy
  6. have least atomic size in Period 3 
Solution 12

(a) G (due to the smallest atomic size).
(b) G and O as both have outermost electronic configuration np5.
(c) A and I as both have outermost electronic configuration ns1.
(d) D (1s22s22p2)
(e) I as alkali metals have least ionisation energy. Also, ionisation energy decreases with an increase in the atomic size that    decreases on moving down the group.
(f) O, as halogens have the least atomic size. 

Question 13

A group of elements in the Periodic Table are given below (boron is the first member of the group and thallium is the last).

Boron, Aluminium, Gallium, Indium, Thallium

Answer the following questions in relation to the above group of elements:

(a) Which element has the most metallic character?

(b) Which element would be expected to have the highest electronegativity?

(c) If the electronic configuration of aluminium is 2,8,3, how many electrons are there in the outer shell of thallium?

(d) The atomic number of boron is 5. Write the chemical formula of the compound formed when boron reacts with chlorine.

(e) Will the elements in the group to the right of this boron group be more metallic or less metallic in character? Justify your answer.

Solution 13

(a) Thallium. Because the metallic character increases down the group, thallium will have the most metallic character.

(b) Boron. Electronegativity decreases down the group as the size increases; hence, boron will be the most electronegative atom.

(c) Three. The number of electrons present in the valence shell is the same for each group. Hence, all these elements and thallium will have 3 valence electrons.

(d) BCl3

(e) Since metallic character decreases from left to right and non-metallic character increases from left to right, elements in the group to the right of this boron group will be less metallic in character.

Chapter 1 - Periodic Table, Periodic Properties and Variations of Properties Excercise Ex. 1

Question 1

Among Period 2 elements A, B, C and D, the one which has high electron affinity is

  1. Lithium
  2. Carbon
  3. Fluorine
  4. Neon 
Solution 1

Correct option is A. Lithium

In a period from left to right, electron affinity decreases as the non-metallic character increases.

Question 2

Group No.'s

 

IA

IIA

IIIA

IVA

VA

VIA

VIIA

0

1

2

13

14

15

16

17

18

Li

 

D

 

 

O

J

Ne

A

Mg

E

Si

 

H

K

 

B

C

 

F

G

 

 

L

 

Select from the table:

  1. Which is the most electronegative?
  2. How many valence electrons are present in G?
  3. Write the formula of the compound between B and H.
  4. In the compound between F and J, what type of bond will be formed?
  5. Draw the electron dot structure for the compound formed between C and K. 
Solution 2
  1. The most electronegative is J.
  2. Valence electrons present in G are 5.
  3. B contains 1 valence electron and H contains 6 valence electrons. So, the valency of B is +1 and the valency of H is - 2.
  4. In the compound between F and J, the type of bond formed will be covalent.
  5. The electron dot structure for the compound formed between C and K is

  

Question 3

The number of electrons in the valence shell of a halogen is ………. A - 1, B - 3, C - 5, D - 7.

Solution 3

The number of electrons in the valence shell of a halogen is 7.

Correct option: D

Question 4

Electronegativity across the period ............ [increases/decreases].

Solution 4

Electronegativity across the period increases.

Question 5

Non-metallic character down the group ………… [increases/decreases].

Solution 5

Non-metallic character down the group decreases.

Question 6

Atomic number of an element is 16. State

  1. to which period it belongs
  2. the number of valence electrons in the element
  3. is the element metal or non-metal 
Solution 6

Atomic number of an element is 16.

  1. It belongs to Period 3.
  2. The number of valence electrons in the element is 6.
  3. The element is a non-metal.
Question 7

Give reasons - The oxidising power of elements increases from left to right along a period.

Solution 7

The oxidising power of elements depends on the tendency to gain electrons which increases from left to right along a period due to increase in nuclear pull.

Question 8

Select the correct answer:

  1. Across a period, the ionisation potential ………… [increases, decreases, remains same]
  2. Down the group, electron affinity ………… [increases, decreases, remains same] 
Solution 8
  1. Across a period, the ionisation potential increases.
  2. Down the group, electron affinity decreases. 
Question 9

Choose the correct answer from the choice given:

In the periodic table, alkali metals are placed in the group A : 1, B : 11, C : 17, D : 18.

Solution 9

In the periodic table, alkali metals are placed in Group I. So, the correct option is A.

Question 10

Choose the correct answer from the choice given:

Which of the following properties do not match with elements of the halogen family?

  1. They have seven electrons in their valence shell.
  2. They are highly reactive chemically.
  3. They are metallic in nature.
  4. They are diatomic in their molecular form. 
Solution 10

 The correct option is C.

The elements of halogen family are non-metallic in nature.

Question 11

State the group and period of the element having three shells with three electrons in the valence shell.

Solution 11

Three shells indicate that the element belongs to the third period.

Three valence electrons indicate that the element belongs to the third group.

Question 12

Choose the correct answer from the option:

An element in Period 3 whose electronic affinity is zero.

  1. Neon
  2. Sulphur
  3. Sodium
  4. Argon 
Solution 12

Correct option: (D) Argon

Question 13

Give reason:

  1. Ionisation potential of the element increases across a period.
  2. Alkali metals are good reducing agents. 
Solution 13

 

  1. Because the atomic radius decreases across a period. Due to this, attraction between the nucleus and the electron increases. This results in an increase in the ionisation potential.

 

  1. Alkali metals are good reducing agents because they have a greater tendency to lose electrons. 
Question 14

There are three elements E, F, G with atomic numbers 19, 8 and 17 respectively.

Classify the above elements as metals and non-metals.

Solution 14

 

Electronic configuration of E with atomic number 19 = 1s22s22p63s23p64s1

E is a metal.

 

Electronic configuration of F with atomic number 8 =

1s22s22p4

F is a non-metal.

 

Electronic configuration of G with atomic number 17 =

1s22s22p63s23p5

G is a non-metal.

Question 15

Name: A metal present in Period 3, Group I of the periodic table.

Solution 15

A metal present in Period 3, Group I of the periodic table is sodium.

Question 16

Among the Period 2 elements, the element which has high electron affinity is

  1. Lithium
  2. Carbon
  3. Chlorine
  4. Fluorine  
Solution 16

Correct option: (D) Fluorine

Question 17

Identify: The element which has the highest ionisation potential.

Solution 17

The element which has the highest ionisation potential is helium (He).

Question 18

 

Group No.

1-1A

2-IIA

13-IIIA

14-IVA

15-VA

16-VIA

17-VIIA

18-0

2nd period

Li

 

D

 

 

O

J

Ne

3rd period

A

Mg

E

Si

 

H

M

 

4th period

R

T

I

 

Q

U

 

Y

 

In the above table, H does not represent hydrogen. Some elements are given in their own symbol and position in the periodic table while others are shown with a letter. Answer the following questions.

  1. Identify the most electronegative element.
  2. Identify the most reactive element of Group I.
  3. Identify the element from Period 3 with least atomic size.
  4. How many valence electrons are present in Q?
  1. Which element from group 2 would have the least ionisation energy?
  2. Identify the noble gas of the fourth period.
  3. In the compound between A and H, what type of bond would be formed and give its molecular formula. 
Solution 18
  1. I
  2. R
  3. M
  4. 5
  5. T
  6. Y
  7. Ionic bond will be formed and the molecular formula is A2H. 
Question 19

Choose the correct answer from the choice given:

 i. Ionisation potential increases over a period from left to right because the

  1. Atomic radius and nuclear charge increase
  2. Atomic radius and nuclear charge decrease
  3. Atomic radius increases and nuclear charge decreases
  4. Atomic radius decreases and nuclear charge increases  

 

 ii. An element A belonging to Period 3 and Group II will have

  1. 3 shells and 2 valence electrons
  2. 2 shells and 3 valence electrons
  3. 3 shells and 3 valence electrons
  4. 2 shells and 2 valence electrons 

 

Solution 19
  1. Correct option: D (atomic radius decreases and nuclear charge increases)
  2. Correct option: A (3 shells and 2 valence electrons) 
Question 20

(b) An atomic number of an element Z is 16. Answer the following:

  1. State the period and group to which Z belongs.
  2. Is Z a metal or a non-metal? 
Solution 20

(a) An element Z having atomic number 16 is Sulphur.

  (i) Sulphur belongs to Period 3 and Group 16.
  (ii) Sulphur is a non-metal.

Question 21

State the formula of the compound between Z and hydrogen.

Solution 21

Two hydrogen atoms combine with one sulphur atom to form hydrogen sulphide (H2S) gas.

Question 22

M is a metal above hydrogen in the activity series and its oxide has the formula M2O. This oxide, when dissolved in water, forms the corresponding hydroxide which is a good conductor of electricity. In the above context, answer the following:

  1. What kind of combination exists between M and O?
  2. State the number of electrons in the outermost shell of M.
  3. Name the group to which M belongs. 
Solution 22
  1. Ionic bond exists between M and O.
  2. 1 electron is present in the outermost shell of M.
  3. M belongs to Group 1 in the modern periodic table. 
Question 23

Give one word or phrase for: The amount of energy released when an atom in the gaseous state accepts an electron to form an anion.

Solution 23

Electron affinity

Question 24

Match the option A and B with the statements (i) and (ii):

 

A. metal

(i) The metal that forms two types of ions

B. iron

(ii) An element with electronic configuration 2, 8, 8, 3

 

Solution 24

A: (ii)

B: (i)

Question 25

Among the elements given below, the element with the least electronegativity is

(i) Lithium

(ii) Carbon

(iii) Boron

(iv) Fluorine

Solution 25

(i) Lithium

Reason: Electronegativity increases from left to right. Lithium is present on the left side of the periodic table; hence, it will be the least electronegative element.

Question 26

The metals of Group 2 from top to bottom are Be, Mg, Ca, Sr and Ba.

(i) Which of these elements will form ions most readily and why?

(ii) State the common feature in the electronic configuration of all these elements.

Solution 26

(i) Ba metal will form ions readily because the ionisationenergy decreases down the group as the size increases.

(ii) On moving down the group, the number of electrons in the outermost shell, i.e.valence electrons remain the same. So, the valency in a group remains the same, i.e. 2.

Question 27

Metals are good _____________ (oxidising agents/reducing agents) because they are electron __________ (acceptors/donors).

Solution 27

Metals are good reducing agents because they are electron donors. 

Question 28

An element with the atomic number 19 will most likely combine chemically with the element whose atomic number is :

A. 17

B. 11

C. 18

D. 20 

Solution 28

(A) 17

Element with atomic number 19 will lose 1 electron (to achieve the noble gas configuration) which can be accepted by the element with atomic number 17. 

Question 29

Rewrite the following sentences by using the correct symbol > (greater than) or < (less than) in the blanks given :

1. The ionization potential of potassium is _________________ that of sodium.

2. The electronegativity of lodine is ___________ that of Chlorine. 

Solution 29

1. less than

2. less than

Question 30

Fill in the blanks by selecting the correct word from the brackets :

i. If an element has a low ionization energy then it is likely to be ______________ (metallic / non-metallic).

ii. If an element has seven electrons in its outermost shell then it is likely to have the ______________ (largest / smallest) atomic size among all the elements in the same period. 

Solution 30

i. Metallic

ii. Smallest 

Question 31

In Period 3 of the Periodic table, element B is placed to the left of element A. On the basis of this information, choose the correct word from the brackets to complete the following statements:

i. The element B would have (lower /higher) metallic character than A.

ii. The element A would probably have (lesser / higher) electron affinity than B.

iii. The element A would have (greater /smaller) atomic size than B. 

Solution 31

i. The element B would have higher metallic character than A.

ii. The element A would probably have higher electron affinity than B.

iii. The element A would have smaller atomic size than B. 

Question 32

Name an

(a) An alkali metal in period 3 and halogen in period 2

(b) The noble gas with 3 shells

(c) The non-metals present in period 2 and metals in period 3.

(d) The element of period 3 with valency 4.

(e) The element in period 3 which does not form an oxide.

(f) The element of lower nuclear charge out of Be and Mg.

(g) Which has higher E.A. Fluorine or Neon?

(h) Which has maximum metallic character Na, Li or K?

Solution 32

(a) Na and F

(b) Argon

(c) C, N, O and F are non-metals present in period 2 while Na, Mg and Al are metals in period 3.

(d) Silicon

(e) Argon

(f) Mg

(g) Fluorine

(h) K

Question 33

Choose the most appropriate answer from [SO2, SiO2, Al2O3, CO, MgO, Na2O]

  1. A covalent oxide of a metalloid.
  2. An oxide which when dissolved in water forms acid.
  3. A basic oxide.
  4. An amphoteric oxide. 
Solution 33
  1. A covalent oxide of a metalloid. - SiO2 (Si is a metalloid)
  2. An oxide which when dissolved in water forms acid. - SO2 (SO2 + H2O H2SO3)
  3. A basic oxide. - Na2O (Na2O + H2O 2NaOH)
  4. An amphoteric oxide. - Al2O3 (shows both acidic and basic properties) 
Question 34

Arrange the following as per instructions given in the brackets.

  1. Mg, Cl, Na, S, Si (increasing order of atomic size)
  2. Cs, Na, Li, K, Rb (increasing metallic character)
  3. Na, K, Cl, S, Si (increasing ionisation potential)
  4. Cl, F, Br, I (increasing electron affinity)
  5. Cs, Na, Li, K, Rb (decreasing electronegativity) 
Solution 34

a. Mg, Cl, Na, S, Si (increasing order of atomic size) -

 

 Cl < S < Si < Mg < Na

 99 pm < 104 pm < 117 pm < 160 pm < 186 pm

 

b. Cs, Na, Li, K, Rb (increasing metallic character)

 

    Li < Na < K < Rb < Cs

 

c. Na, K, Cl, S, Si (increasing ionisation potential) -

 

 Cl < S < Si < Na < K

 1256 < 999 < 786 < 496 < 419


d. Cl, F, Br, I (increasing electron affinity) -

 

 I < Br < F < Cl

 -295 KJ mol-1 < -324 KJ mol-1 < -327.9 KJ mol-1 < -349 KJ mol-1


e. Cs, Na, Li, K, Rb (decreasing electronegativity) -

 

 Li > Na > K = Rb > Cs

 1.0 > 0.9 > 0.8 = 0.8 > 0.7

Question 35

Chorine in the periodic table is surrounded by the elements with atomic number 9, 16, 18 and 35.

(a) Which of these have physical and chemical properties resembling chlorine?

(b) Which is more electronegative than chlorine?

Solution 35

(a) An element with atomic number 9 and 35

(b) An element with atomic number 9.

Question 36

First Ionization enthalpy of two elements X and Y are 500 kJ/mol-1 and 375 kJ /mol-1 respectively. Comment about their relative position in a group as well in a period.

Solution 36

 

The ionisation energy is the minimum energy required to remove the outermost electron from a gaseous neutral atom to form a cation.

Position in a group: X will be above Y ( because of ionisation energy decreases down the group )

Position in a period: X will be the right side of Y ( because ionisation energy increases from left to right)

Question 37

Arrange the following in order of increasing radii:

(a) Cl¯, Cl

(b) Mg2+, Mg, Mg+

(c) N, O, P

Solution 37

(a) Cl < Cl¯

(b) Mg2+ < Mg+ < Mg

(c) O < N < P

Question 38

Which element from the following has the highest ionization energy?

(a) P, Na, Cl

(b) F, O, Ne

(c) Ne, He, Ar

Explain your choice.

Solution 38

(a) Cl

Metals have low ionisation energy and non-metals have high ionisation energy. Also, across the period, ionisation energy tends to increase. The elements P, Na and Cl belong to the third period. Na - Group 1, P - Group 15 and Cl - Group 17.

(b) Ne

Inert gases have zero electron affinity because of their stable electronic configuration.

(c) He

Ionisation energy decreases with an increase in the atomic size, i.e. it decreases as one moves down a group. Ne, He and Ar are inert gases. He - Period 1, Ne - Period 2 and Ar - Period 3.

Question 39

The electronegativities(according to Pauling) of the elements in period 3 of the periodic table are as follows with elements arranged in alphabetical order:

Al

Cl

Mg

Na

P

S

Si

1.5

3

1.2

0.9

2.1

2.5

1.8

Arrange the elements in the order in which they occur in the periodic table from left to right.

(The group 1 element first, followed by the group 2 element and so on, up to group 7).

Solution 39

Na, Mg, Al, Si, P, S, Cl

Question 40

Choose the word or phrase from the brackets which correctly completes each of the following statements:

  1. The element below sodium in the same group would be expected to have a ............... (lower/higher) electro-negativity than sodium, and the element above chlorine would be expected to have a (lower/higher) ionisation potential than chlorine.
  2. On moving from left to right in a given period, the number of shells ................. (remains the same/increases decreases).
  3. On moving down a group, the number of valence electrons .................. (remains the same/increases/decreases).
  4. Metals are good ................. (oxidising agents/reducing agents) because they are electron ............. (acceptors/donors). 
Solution 40

(a)  The element below sodium in the same group would be expected to have a lower electro-negativity than sodium, and the element above chlorine would be expected to have a higher ionisation potential than chlorine.


(b) On moving from left to right in a given period, the number of shells remains the same.


(c) On moving down a group, the number of valence electrons remains the same.


(d) Metals are good reducing agents because they are electron donors. 

Question 41

Parts (a) to (e) refer to change in the properties of elements on moving from left to right across a period of the periodic table. For each property, choose the correct answer.

(a) The non-metallic character of the elements:

(i) Decreases

(ii) Increases

(iii) Remains the same

(iv) Depends on the period

(b) The electronegativity:

(i) Depends on the number of valence electrons

(ii) Remains the same

(iii) Decreases

(iv) Increases

(c) The ionization potential:

(i) goes up and down

(ii) Decreases

(iii) Increases

(iv) Remains the same

(d) The atomic size:

(i) Decreases

(ii) Increases

(iii) Remains the same

(iv) Sometimes increases and sometimes decreases

(e) The electron affinity of elements in group 1 to 7 :

(i) Goes up and then down

(ii) Decreases and then increases

(iii) Increases

(iv) Decreases

Solution 41

(a) Increases

(b) Increases

(c) Increases

(d) Decreases

(e) Increases

Question 42

The elements of one short period of the periodic table are given below in order from left to right:

Li Be B C O F Ne

(a) To which period do these elements belong?

(b) One element of this period is missing. Which is the missing element and where should it be placed?

(c) Place the three elements: Fluorine, Beryllium and nitrogen in the order of increasing electronegativity.

(d) Which one of the above element belongs to the halogen series?

Solution 42

(a) Period 2

(b) Nitrogen (N), between carbon and oxygen

(c) Be< N< F

(d) Fluorine

Question 43

Select the correct answer from the choices A, B, C, D which are given. Write down only the letter corresponding to correct answer.

With reference to the variation of properties in the Periodic table, which of the following is generally true?

A Atomic size increases from left to right across a period.

B Ionization potential increases from left to right across a period.

C Electron affinity increases going down a group.

D Electro-negativity increases going down a group.

Solution 43

B

Key Features of Study Materials for ICSE Class 10 Chemistry:

  • According to the latest ICSE syllabus
  • Prepared by subject matter experts
  • Helpful for quick revision
  • Free solved sample papers available
  • Significantly improve your marks