Question

The number of valence electrons present in $Ca$ atom are-
A. 3
B. 2
C. 8
D. 6

Answer 1

Hint: It is an s-block element, belonging to group 2 and period IV. Calcium is an alkaline earth metal, having atomic number 20. Its chemical symbol is $Ca$.

Complete step by step answer:
It has 20 electrons arranged in electron configuration $\left[Ar\right]4s^2$ . Since, it lies in group 2 of the periodic table of s-block, so it has 2 electrons in its outermost shell, like other s-block elements.
Valency can be defined as the number of electrons which an atom can lose, gain or share in order to attain stable electronic configuration. There are mainly two ways to add electrons to an atom to attain stability, duplet rule or octet rule, according to which it can gain stability if there are 2 electrons in valence shell or an atom will be stable if it has 8 electrons in its valence shell. . In case of calcium, we will apply octet rule, as per its electronic configuration.

So, the correct option is B.

Note:
-Do not confuse between valency and oxidation number. Valency tells about the number of electrons an atom can gain, lose or share so that no charge will be present whereas oxidation state consists of a charge that signifies either the atom has lost an electron or gained an electron.
-Due to strong affinity for oxygen and sulfur, calcium is widely used in steelmaking.
-There are certain dairy products which are rich in calcium such as yogurt, cheese and are also present in salmon , soy products.