First ionisation enthalpy values of first four group 15 elements are given below. Choose the correct value for the element that is a main component of apatite family :

<p>Apalite family - A group of phosphate minerals that includes fluorapatite, chlorapatite, and hychoxyapatite. Chemical formula $C{a_{10}}{(P{O_4})_6}{(OH,F,Cl)_2}$</p> <p>$$\left. \matrix{ Fluorapatite \to C{a_{10}}{(P{O_4})_6}{F_2} \hfill \cr Chlorapatite \to C{a_{10}}{(P{O_4})_6}C{l_2} \hfill \cr Hydroxyapatite \to C{a_{10}}{(P{O_4})_6}{(OH)_2} \hfill \cr} \right\}\matrix{ {Main\,components:} \cr {Calcium\,and\,phosphate} \cr }$$</p> <p>So, the element considered is phosphorus.</p> <p>The first four group 15 elements are Nitrogen (N), Phosphorus (P), Arsenic (As) and Antimony (Sb). The outer configuration of phosphorus is half filled and hence stable $({s^2}{p^3})$.</p> <p>For a stable configuration, ionization enthalpy is high. Ionization enthalpy - Energy required to remove an electron from the gaseous atom.</p> <p>Nitrogen has the highest first ionization enthalpy in group 15.</p> <p>Down the group, ionization enthalpy decreases.</p> <p>Down the group, atomic size increases, valence electrons are less attracted to the nucleus. And here, electron removal will become easier. So, ionization enthalpy is also decreases.</p> <p>The highest value of ionization enthalpy 1402 KJ mol$^{-1}$ corresponds to nitrogen element.</p> <p>So, the first ionization enthalpy of the element that is a main component of apatite family is option D) 1012 kJ mol$^{-1}$.</p>