Question

Match the atomic number 2, 4, 8, 15, and 19 with each of the following: [5]
(i) A solid non-metal belonging to the third period.
(ii) A metal of valency 1.
(iii) A gaseous element with valency 2.
(iv) An element belonging to Group 2.
(v) A rare gas

Answer 1

A solid non metal belonging to the third period = 15
A metal of valency 1 = 19
A gaseous element with valency 2 = 2
An element belonging to group 2= 4 and
A rare gas = 18

Answer 2

( i ) Element with atomic number 15

( ii ) Element with atomic number 19

( iii ) Element with atomic number 8

( iv ) Element with atomic number 4

( v ) Element with atomic number 2

• Atomic number is the number of protons ( positive charged particles ) in the nucleus of an atom.

• In a neutral atom, the number of protons ( Atomic Number ) is equal to the number of electron.