(a)[3]
A phosphide ion may be represented by $^{31}_{15}\text{P}^{3-}$. Complete Table 4.1 to show the number of particles in this phosphide ion.
(b)[1]
State why a phosphide ion is written as $\text{P}^{3-}$ instead of $\text{P}^{2-}$ or $\text{P}^{4-}$.
(c)[1]
A calcium ion has the formula $\text{Ca}^{2+}$. Deduce the formula of calcium phosphide.
(d)[2]
Calcium phosphate, $\text{Ca}_3(\text{PO}_4)_2$, is an ionic compound. Explain why calcium phosphate melts at a high temperature.
(e)[2]
Calculate the mass percentage of phosphorus in calcium phosphate. Give your answer to two significant figures.