FRANK Solutions for Class 9 Chemistry Chapter 7 - Atomic Structure

Page / Exercise

Chapter 7 - Atomic Structure Exercise 113

Question 1
Compare the characteristics of an electron, proton and neutron.
Solution 1
Frank Solutions Icse Class 9 Chemistry Chapter - Atomic Structure
Question 2
Frank Solutions Icse Class 9 Chemistry Chapter - Atomic Structure
Solution 2
Frank Solutions Icse Class 9 Chemistry Chapter - Atomic Structure
Question 3
Name the constituent particles in the atom that determine the following:
(a) Mass of an atom
(b) Size of an atom
Solution 3
(a) Mass of an atom - Protons and neutrons
(b) Size of an atom - Electrons
Question 4
Name three fundamental particles of an atom.
Solution 4
Three fundamental particles of an atom are-
(a) Proton
(b) Electron
(c) Neutron
Question 5
Define(a) an atom, (b)an element.
Solution 5
(a) An atom - An atom is the smallest particle of an element which may or may not be capable of independent existence.
(b) An element - An element is usually defined as a pure substance that contains only one kind of particles. These particles may be atoms or molecules.
Question 6
What do you mean by the term atomic number and which letter is used to represent it?
Solution 6
Atomic number - The number of protons present in the nucleus of an atom is called the atomic number of the atom.
It is denoted by 'Z'.
Question 7
What are nucleons?
Solution 7
The protons and neutrons are collectively called as nucleons.
Question 8
What are isotopes? Name three isotopes of hydrogen.
Solution 8
Isotopes are atoms of the same element, having the same atomic number, same chemical properties but different mass number, i.e., the atoms differ in the number of neutrons. The three isotopes of hydrogen atoms are-
(i) Protium
(ii) Deuterium
(iii) Tritium
Question 9
Why do isotopes of an element have the same chemical properties?
Solution 9
Electrons take part in a chemical reaction. Therefore, the chemical properties of an element depend upon the electronic configuration. Since, isotopes of an element have the same atomic number and hence same electronic configuration. So, they exhibit the same chemical properties.
Question 10
Compare Dalton's atomic theory with Modern Atomic Theory?
Solution 10
Frank Solutions Icse Class 9 Chemistry Chapter - Atomic Structure
Question 11
What is meant by valence shell and valence electron?
Solution 11
The outermost orbit of an element is called valence shell. The electrons present in the outermost orbit (valence shell) of an element are called valence electrons.
Question 12
Why do atoms combine by transferring electrons?
Solution 12
Atoms may have incomplete octet. During the formation of a molecule, an atom of a particular element gains, loses or shares electrons until it acquires a stable configuration of eight electrons in its valence shell.
Question 13
An atom contains 20 protons, 20 electrons and 20 neutrons. Mention the following details of that atom
(a) Atomic number
(b) Mass number
(c) Electronic configuration
(d) Valency
Solution 13
(a) Atomic number = Number of protons = 20      
(b) Mass number = Number of protons +Number of electrons = 20 + 20 = 40
(c) Electronic configuration = 2, 8, 8, 2
(d) Valency = 2
Question 14
Frank Solutions Icse Class 9 Chemistry Chapter - Atomic Structure
(a) What is the valency of each of these five atoms?
(b) Which of these contains the greatest number of neutrons?
(c) Which of these contains the least number of electrons?
(d) Which of these contains equal number of electrons and neutrons?
(e) Which of them is a metal?
(f) Which is the most reactive of the non-metals?
(g) What is common between C and D?
(h) Which of them belongs to a particular family?
(i) If atoms of A combines with atoms of B, what will be the formula of the compound formed?
(j) By what type of valency will B and C combine?
Solution 14
(a) A=1
B=3
C=2
D=1
E=1
(b) E contains the greatest number of neutrons.
(c) A contains the least number of electrons.
(d) B contains equal number of electrons and neutrons.
(e) A is a metal.
(f) Fluorine is the most reactive of the non-metals.
(g) Both are electronegative and non-metals.
(h) D and E belongs to a particular family.
(i) A3B will be the formula if atoms of A combines with atoms of B.
(j) 'B' will combine in  a trivalent  element while 'C' will combine as a bivalent element.

Chapter 7 - Atomic Structure Exercise 114

Question 15
What is the octet rule?
Solution 15
"During the formation of the molecule, an atom of a particular element gains, loses electrons or shares electrons until it acquires a stable configuration of eight electrons in its valence shell" i.e. until it acquires octet.
Question 16
What are the maximumnumber of electrons that the K, L and M shells can accommodate?
Solution 16
K can accommodate maximum of 2 electrons.
L can accommodate maximum of 8 electrons.
M can accommodate maximum of 18 electrons.
Question 17
Name the rays which are formed at the negative electrode of the discharge tube experiment?
Solution 17
Cathode rays are formed at the negative electrode of the discharge tube experiment.
Question 18
Calculate the maximum number of electrons which can be accommodated in (i) K, (ii) L (iii) M and (iv) N-shells
Solution 18
(i) In K maximum number of 2 electrons can be accommodated.
(ii) In L maximum number of 8 electrons can be accommodated.
(iii) In M maximum number of 18 electrons can be accommodated.
(iv) In N maximum number of 32 electrons can be accommodated.
Question 19
Frank Solutions Icse Class 9 Chemistry Chapter - Atomic Structure
Solution 19
Frank Solutions Icse Class 9 Chemistry Chapter - Atomic Structure
Question 20
Magnesium (atomic number 12) is a metallic element. Find its valency.
Solution 20
Electronic configuration of magnesium is -2, 8, 2. Since, it has 2 electrons in its valence shell, so its valency is 2.
Question 21
The atomic number and mass number of sodium are 11 and 23 respectively. What information is conveyed by this statement?
Solution 21
Number of electrons in Sodium = 11
Number of protons in sodium = 11
Number of neutrons in sodium = 12
Number of nucleons in sodium = 23
Question 22
What are inert elements? Why do they exist as monoatoms in molecule?
Solution 22
Inert elements are the elements which have completely filled valence shell. Since, they are already stable and do not need more electrons, they do not combine with other atoms. So, they exist as monoatoms in molecule.
Question 23
Name or state the following:
(a) The element which does not contain any neutron in its nucleus.
(b) The shell closest to the nucleus of an atom.
(c) Metal with valency 2.
(d) Two elements having same number of protons and electrons but different number of neutrons.
(e) An element having valency 'zero'.
Solution 23
(a) Hydrogen
(b) K shell.
(c) Magnesium
(d) Isotopes
(e) Helium has zero valency.
Question 24
Frank Solutions Icse Class 9 Chemistry Chapter - Atomic Structure
Solution 24
(a) The number of protons = 9
(b) The number of neutrons = 19 - 9 = 10
(c) The number of electrons = 9
Question 25
Atomic number is unique to an atom, but the mass number is not. Explain this briefly.
Solution 25
Atomic number is the number of protons of an atom which is unique to an atom but mass number is the total of number of protons and number of neutrons which may or may not be same to other atoms since there is probability of combination of number of protons and number of neutrons be same for two atoms.