# Question #18660

May 1, 2017

Phosphorus can have both a positive and a negative valency.

#### Explanation:

If phosphorus combines with a metallic element it has a negative valance. The phosphorus because it has a higher electron negativity than the metals will act as an oxidizer taking electron away from the positive metals. This creates a valance of -3

If phosphorus combines with a non metal element with a higher electron negativity than phosphorus it will have a positive valance.

When phosphorus combines with Oxygen to form an phosphate ion it has a charge of +5 $P {O}_{3}^{-} 1$ This is because Oxygen will act as the oxidizer taking the electrons away from the phosphorus.

Phosphorus can have either a positive valance or a negative valance depending on what other element it is combining with and the relative electron negativity of the other elements.

Jul 15, 2017

Valency is the number of $\text{H}$ atoms or $\text{Cl}$ atoms that can form bonds to a particular element.
Thus, in ${\text{PH}}_{3}$ and in ${\text{PCl}}_{3}$ the valency of phosphorus is 3.
In ${\text{PCl}}_{5}$ the valency of phosphorus is 5.