Question

Which of the following has zero valency
A. Sodium
B. Beryllium
C. Aluminium
D. Krypton

Answer 1

Hint: The combining capability of an atom is its valency. It expresses the no.of bonds that an atom can constitute as part of a compound. Valence electrons exist in the outer orbit of the atom.

Complete Step by Step Solution:
In this question, we have to find out which of the following elements have zero valencies.

We know that valency is the tendency of an atom to combine with another atom. An element that has zero valency does not combine with other atoms or does not form compounds.

Krypton is the element of Group 18 of the modern periodic table. All the members of this family have gaseous forms and are known as noble gases. They exhibit low chemical reactivity as they maintain stable electron configurations. They have a stable octet. Due to this, they do not constitute molecules readily and largely exist as monatomic gases.

The valence shell of Krypton is filled i.e. form an octet. These gases exhibit inactive behaviour. In the bond formation, they neither gain nor lose an electron so they don't take part in the bond formation. Hence, the valency of group 18 is deemed as 0. So, Krypton has zero valencies.
So, option D is correct.

Note: If the outermost shell carries 8 electrons then the element has a complete octet. Elements earn, share, or lose the electrons the atoms achieve a stable octet. The ability of an atom is depicted by the entire number of electrons eliminated, earned, or shared to complete its octet which also specifies the valency of the atom.