# How do you find the atomic mass number of phosphate?

Jun 29, 2016

$P {O}_{4}^{-} 3 = 94.93$amu

#### Explanation:

Phosphate is a polyatomic ion with a formula of $P {O}_{4}^{-} 3$

This molecule has one atom of Phosphorus and 4 atoms of Oxygen.

$P - 1 \cdot 30.97 = 30.97$
$O - 4 \cdot 15.99 = 63.96$

$30.97 + 63.96 = 94.93$

$P {O}_{4}^{-} 3 = 94.93$amu