A polyatomic ion can be formed from two or more atoms of same or different elements.
Name or state the following :
(a) An element having valency zero.
(b) Metal with valency one.
(c) Atoms of the same element differing in mass numbers.
(d) Elements having same mass number but different atomic number.
(e) Bond formed by transfer of electron(s).
(f) Ion formed by gain of electron(s).