Question

The formula of calcium phosphate is Ca3(PO4) 2 use this formula to deduce the charge on the phosphate ion

Answer 1

We have to deduce the charge on the phosphate ion from the calcium phosphate, Ca₃(PO₄)₂.

solution : calcium phosphate is ionic compound where calcium is cation and phosphate is anion.

calcium is a metal and we know, metals have tendency to loss electron from its outermost shell.

from configuration of Calcium = 1s², 2s² , 2p⁶ , 3s², 3p⁶ , 4s² = 2, 8, 8, 2

we see, in outermost shell only two electrons are present. so calcium loses its two electron and forms Ca²⁺ ion.

now we know, charge on Ca²⁺ ion is +2.

let charge on phosphate ion is x

as net charge on compound is zero.

so, 3 × (+2) + 2 × x = 0

⇒x = -3

Therefore charge on phosphate ion is -3. i.e., (PO₄)³¯