Which of the following elements exhibits a valency of $2$?

The oxidation states of phosphorus vary from

The most common oxidation state of an element is $-2$. The number of electrons present in its outermost shell is

Predict the formulas of the stable binary compounds that would be formed by the combination of the following pairs of elements.
$(a)$ Lithium and oxygen
$(b)$ Magnesium and nitrogen
$(c)$ Aluminium and iodine
$(d)$ Silicon and oxygen
$(e)$ Phosphorus and fluorine
$(f)$ Element $71$ and fluorine

Which one of the following elements shows both positive and negative oxidation states?

The oxidation state of $I$ in $IPO_4$ is