Which of the following pair of elements will show valency = 3A P and N B S and Cl C O and F D F and I

The valency of an element is determined by the number of electrons in the outermost shell of its atoms. It is the combining capacity of an element.

A. P (Phosphorus) and N (Nitrogen) Phosphorus (P) has 5 electrons in its outermost shell and Nitrogen (N) has 5 electrons in its outermost shell. So, their valency is not 3.

B. S (Sulfur) and Cl (Chlorine) Sulfur (S) has 6 electrons in its outermost shell and Chlorine (Cl) has 7 electrons in its outermost shell. So, their valency is not 3.

C. O (Oxygen) and F (Fluorine) Oxygen (O) has 6 electrons in its outermost shell and Fluorine (F) has 7 electrons in its outermost shell. So, their valency is not 3.

D. F (Fluorine) and I (Iodine) Fluorine (F) has 7 electrons in its outermost shell and Iodine (I) has 7 electrons in its outermost shell. So, their valency is not 3.

Therefore, none of the given pairs of elements have a valency of 3.