In the following table the mass number and the atomic number of certain elemnts are given:

(a)Select the pair of isobars from the above table.
(b) What would be the valency of the element C listed in a neutrl atom?
(c ) Which two sub atomic particles are equal in number in a neutral atom?

Explanation

(a) Element D and E are pari of isobars since they have same mass no =40
(b) The electronic configruation of the element C with Z= 2,5 .It has five valence elecrtrons.Its valecy can be either 5 or 3 (8-5) =3
(c ) In a neutral atom the number of elctrons in the extra nuclear portion is equal to the number of protons in the nucleus