Valency

State Octet rule.

The valency of oxygen is $3$ in the water molecule.

Define the following terms.

Valency 

The combining capacity of an element is called its atomicity.

What is the valency of sodium in $\mathrm{NaCl}$ and calcium in $\mathrm{CaO}$?

Elements with valency 1 are either metals or_____.

The valency of iodide ion is _____.

The Valency of Hydroxide ion is _____.

The common valency of lead is 1 and_____.

The valency of fluoride ion is _____ .

The valency of the Barium ion is _____.

The valency of potassium ion is _____.

What is the general name of the elements having $8$ electrons in the valence shell of their atoms?

Choose from the following list, as to what matches the descriptions below:

$\left[\left(\mathrm{A}\right) {\mathrm{O}}^{2-} \left(\mathrm{B}\right) {\mathrm{O}}_2 \left(\mathrm{C}\right) {{\mathrm{NH}}_4}^{+} \left(\mathrm{D}\right) {\mathrm{OH}}^{-} \left(\mathrm{E}\right) {\mathrm{H}}_2\mathrm{O} \left(\mathrm{F}\right) {\mathrm{NH}}_4\mathrm{Cl} \left(\mathrm{G}\right) \mathrm{HCl} \left(\mathrm{H}\right){\mathrm{Ca}}^{2+} \left(\mathrm{I}\right) \mathrm{MgO} \left(\mathrm{J}\right) {\mathrm{Ca}}^{2+}\right]$

A cation whose electronic configuration resembles argon.

Enter your answer as $\mathrm{A}, \mathrm{B}, \mathrm{C}, \mathrm{D}, \mathrm{E}, \mathrm{F}, \mathrm{G}, \mathrm{H}, \mathrm{I}$ or $\mathrm{J}$