Question

Valency of an element is the number of electrons_______ by an atom.
A. Lost
B. Gained
C. Shared
D. Any of these

Answer 1

Hint: Valency is the combining power of an element. The valency of an element is related to how many electrons are in the outer shell. The valency of an element is the number of hydrogen atoms that can combine with or replace (either directly or indirectly) one atom of the element.

Complete step-by-step answer:
The valency of an atom is determined by the number of valence electrons present in the outermost shell of its atom. The number of electrons lost or gained or shared by an atom of element to achieve the nearest inert gas electron configuration, gives us the valency of an element.
So, the answer is “D”
“A” is correct because some elements lose electrons to achieve inert gas configuration. For example Mg, its atomic number is 12 and electronic configuration is 2, 8, 2. So, it can lose 2 valence electrons to achieve configuration of neon (2, 8).
“B” is correct because some elements gain electrons. For example sulphur, it has atomic number 16 and electronic configuration 2, 8, 6. It has two options one is to lose 6 valence electrons and other is to gain 2 electrons to achieve stable inert gas configuration. But it cannot lose 6 electrons because of energy consideration. So, it gains 2 electrons.
“C” is also correct, because some elements share their electrons in covalent bonds to complete their octet or to achieve the nearest inert gas configuration.

Note: There are some elements which show both types of valencies that they lose electrons and also they gain electrons i.e. they can have both positive and negative charge. And in case of shared electrons they do not show complete charge instead they show partial charge.