JEE Main · 2022 · 24 Jun 2022 · Shift 1 · s-Block Elements

Tooth enamel is primarily composed of hydroxyapatite, ${\mathrm{Ca}}_{10}({\mathrm{PO}}_4{)}_6(\mathrm{OH}{)}_2$, containing ${\mathrm{Ca}}^{2+}$ and phosphate (with phosphorus in the +5 oxidation state as ${\mathrm{PO}}_4^{3-}$). Fluoride (${\mathrm{F}}^{-}$) can substitute for hydroxide to form fluorapatite. Phosphorus does not exist as ${\mathrm{P}}^{3+}$ in enamel. Answer: (B) ${\mathrm{P}}^{3+}$.