Question

What is the valency of an element that has atomic number $19$?

• A. $1$
• B. $2$
• C. $8$
• D. $9$

Answer 1

The correct option is A $1$

Valency is the combining capacity of an element.
Electronic configuration of given element is:
$Z=19:2,8,8,1$
It has $1$ electron in its valence shell so it can donate that electron to combine with other elements. Hence its valency is one.