First ionisation enthalpy values of first four group 15 elements are given below. Choose the correct value for the…

🧠 Apatite is a calcium phosphate mineral — its main element is Phosphorus. So you need $IE_1$ of P The apatite family includes minerals like fluorapatite ($\ce{Ca5(PO4)3F}$), chlorapatite, and hydroxyapatite. They are all calcium phosphate minerals — phosphorus is the key element. Question wants $IE_1$ of phosphorus, then match it to one of the four numerical options.

🗺️ Identify the value Group 15 first ionisation enthalpies (kJ/mol): $\ce{N}$ (Period 2): $1402$. $\ce{P}$ (Period 3): $1012$. $\ce{As}$ (Period 4): $947$. $\ce{Sb}$ (Period 5): $834$.

So $IE_1(\ce{P}) = 1012\,kJ/mol$. That matches option (a).

⚠️ Common mistake Option (b) gives 1402 — which is N's IE. Students who don't know that apatite is a phosphate mineral might think the question is about Nitrogen. Apatite contains $\ce{PO4^{3-}}$, not nitrate. Tooth enamel and bones are made of hydroxyapatite — phosphate. Lock this in: apatite ↔ phosphorus.

$\boxed{\text{Answer: (a)}}$