ANSWER:
ATOMICITY:
“The number of atoms present in a molecule is called its atomicity.”
The molecules may be:
- Monoatomic __ consisting of one atom like He, Ne, Ar, Kr, etc.
- Diatomic __ consisting of two atoms like H2, Cl2, HCl, etc.
- Triatomic __ consisting of three atoms like CO2, H2S, etc.
(Ref. An Insight Into Objective Chemsitry-11, Ch-01, Q. No. 07)