(a) What are inert elements ?

(b) Why do they exist as monoatoms in molecules ?

(c) What are valence electrons ?

Q. (i) Why group 17 elements are highly reactive?
(ii) How many electrons do inert gases have in their valence shells?

Q.

(a) What are the usual number of valence electrons and valency of group 18 elements of the periodic table?

(b) What happens to the number of valence electrons in the atoms of elements as we go down in a group of the periodic table?

Q. Assertion :Alkali metals are paramagnetic but their salts are diamagnetic. Reason: Alkali metals are elements having 1 valence electron is s-subshell. As it has one unpaired electron, the salts of alkali metals are formed by bonding of their valence electrons as they do not have unpaired electrons.

Q.

(a) What are valence electrons? Where are valence electrons situated in an atom ?

(b) What is the number of valence electrons in the atoms of an element having atomic number 13 ? Name the valence shell of this atom.

Q.

Assertion: ${}^{20}Ne$ and ${}^{22}Ne$ are isotopes.
Reason: Noble gases do not exist as isotopes as they are inert.