Question

Four atoms are labelled from A to D:

Atoms	Mass No.	Atomic no.
A	19	9
B	7	3
C	16	8
D	14	7

The compound formed when C combines with C?

Answer 1

The formula of a compound depends on the combining capacity of the atoms in that compound.

The combining capacity is called the valency. It can be calculated by counting the valence electrons ( electrons present in the outer shell ).

• If the atom has 4 or less than 4 electrons- the valency us equal to the number of valence electron
• If the atom has more than 4 electrons- the valency is [8-(number of valence electrons)]

Here, the electronic configuration C is- 2,6 . So, the valency of C is- (8-6)=2.

As, both the C atoms will have same valency, so the formula will become ${\mathrm{C}}_2$.