An atom X has 4 protons and 5 neutrons with electronic configuration 2, 2.

Give information about its

(i) atomic number

(ii) mass number

(iii) valency

Describe the essential properties of the atomic nucleus. Compare these with the properties of the electron.

The electronic configurations of some elements are given below. Name the elements.

(i) 2, 8, 5

(ii) 2, 8, 8, 2

(iii) 2, 8, 1

The number of neutrons and protons present in the nuclei of two atomic species A and B are given below.

(i) Write the mass numbers of A and B.

(ii) What is the relation between two species?

(iii) Write the electronic configuration of atoms A and B.

What information do you get from the figure given below about the atomic number, mass number and valency of atom X?