Ar(Ca) = 40

Ar(P) = 31

Ar(O) = 16

Mr(Ca3(PO4)2) = 40×3 + 31×2 + 16×8 = 310

[tex]W = \frac{Ar*n}{Mr}[/tex]   ; n >> кол-во атомов елемента

W(Ca) = (40×3) : 310 × 100% = 38,71 %

W(P) = (31×2) : 310 × 100% = 20 %

W(O) = 100% - (38,71 + 20) = 41,29 %