Parameters Of An Atom Free Doubts and Solutions

(a) How are electrons arranged around the nucleus in an atom.

(b) If an atom of an element has atomic number 11 and mass number 23, find the number of protons, electrons and neutrons in its atoms.

                                                                   OR

(a) The average atomic mass of a sample of an element X is 16.2 u. What are the percentages of isotopes  in the sample?

(b) Complete the following table.

(a)  are symbols of two isotopes of Magnesium. Compare atoms of these isotopes with respect to

(i)Composition of their Nuclei

(ii)Electronic configuration and valency

(b)Give the reason why two isotopes of magnesium have different mass numbers.

The average atomic mass of a sample of an element X is 35.5 u. What are the percentages of isotopes  and  in the sample?

The atomic number of Chlorine is 17 and mass number is 35.

(a) What would be the electronic configuration of negatively charged chlorine ion, Cl^-?

(b) What would be the atomic number and mass number of Cl^-?

(c) Define valency and calculate the valency of Cl^-.  

                                                                         OR

(a) Consider the atom .

(i) What does the figures 5 and 10 indicate?

(ii) How many number of electrons does this element contain?

(iii) The relative atomic mass of Boron is 10.8 u. Calculate the percentage of its isotopes  and , occurring in nature.

(a) Why do the inert gases like neon and argon have zero valency?

(b) The atomic number of sodium is 11 and oxygen is 8. Predict their valencies.

(c) Draw the atomic structure of sulphur .

(d) State the difference between a proton and an electron on the basis of their location.

(e) Give one use of an isotope of cobalt and one use of an isotope of iodine.

                                                                        OR

(a) During radioactive disintegration, an atom gets converted into another atom whose mass number remains the same but atomic number increases by one. Will the new atom formed be an isobar or isotope of the parent atom?

(b) Which is heavier: a proton or an electron and how many times?

(c) How many electrons are present in the outer shell of the atom of a noble gas other than helium?

(d) Write the drawbacks of Rutherford's model.

(a) In Rutherford's experiment, how was it shown that an atom has a lot of empty space within it?

(b) Why is the nucleus of an atom positively charged?

(c) Calculate the valency of chlorine, sulphur and magnesium.

     Atomic number of Chlorine = 17, sulphur = 16, magnesium = 12

                                                                        OR

(a) Oxygen has three isotopes of atomic masses 16, 17 and 18 respectively. Explain the following:

     (i) They have same chemical properties.

     (ii) They are all electrically neutral.

     (iii) Name the isotopes of hydrogen.

     (iv) Give one point of similarity and one point of difference between isotopes .              

(a) Can electrons be arranged in second shell or L shell without filling electrons in first shell or K shell?

(b) The atom of an element X is written as .

    (i) What does the figure 13 indicate?

    (ii) What does the figure 27 indicate?

    (iii) What is the number of protons in the X?

    (iv) What is the number of electrons in X?

                                                                         OR

Give reasons for the following:

(i) Argon and calcium are called isobars.

(i) Helium and neon have zero valency.

(iii) An atom is neutral.

(iv) Nucleus is positively charged.

(v) Isotopes have similar chemical properties.

How is the following pair of atom related?

State the relationship between the atoms given below. Define the term used for this relationship. Write one characteristic feature of such atoms.