Structure of the atom Worksheet-9

Structure of the atom Worksheet-9


  1. The electronic configuration of an element Z is 2, 8, and 6. How many electrons does it require to have a stable configuration?


  1. Which isotope is used in nuclear fuel?


  1. Does 1X3 and  2Y3 represent a pair of isotopes?


  1. Name the elements which have the following electronic configuration :

(i) 2, 6 (ii) 2, 7 (iii) 2, 8, 1 (iv) 2, 8, 7 (iv) 2, 8


  1. Out of L and M shells, which is near to the nucleus of an atom ?


  1. Between two electrons designated as 'A' and 'B', the electron 'A' is experiencing less attraction towards the nucleus. Is it present in lower energy shell as compared to the electron ‘B’?


  1. Define : (A) atomic number, (B) mass number.


  1. Give example of each of the following :

(i) Isotope of 17Cl35, (ii) Isobar of ­20Ca40


  1. Which isotope of hydrogen is known as protium?


  1. Composition of the nuclei of the two atomic species A and B are given :

                             A       B

Protons        =    8       8

Neutrons     =    8       10

Give the mass numbers of A and B. What is the relation between A and B?


  1. If Z = 4, what would be the valency of the element? Also name the element.



  1. In order to have a stable configuration, the element Z must have 8 electrons in the valence shell. It needs (8 - 6) = 2 electrons to complete its octet.


  1. Uranium-235 isotope is used in nuclear fuel.


  1. No, they do not because the two elements differ in their atomic numbers. Isotopes have the same atomic numbers.


  1. (i) Oxygen (ii) fluorine (iii) sodium (iv) chlorine (v) neon.


  1. L-shell


  1. The electrons present in the higher energy shells experience less force of attraction by the nucleus. The closer is the shell to the nucleus the lesser is its energy. Thus electron present in the lower energy shells experience more force of attraction.


  1. (A) The number of protons in one atom of an element is known as its atomic number.

(B) The number of protons in one atom of an element is known as its atomic number.


  1. (i) 17Cl37, (ii) 18Ar20


  1. Ordinary hydrogen (1H1).


  1. Mass no. of A = 8 + 8 = 16; mass no. of B=8+10=18; A and B are isotopes.


  1. The configuration of the element with Z = 4 is given as : 2, 2 . The valency of element is 2. It is beryllium (Be).