Question

Arrange the given elements $S,P,As$ in the order of increasing ionization enthalpy.
a) $S > P > As$
b) $P < S < As$
c) $As < S < P$
d) $As < P < S$

Answer 1

Ionization enthalpy is defined as the amount of energy that is required by an isolated gaseous atom to lose an electron from its ground state. It is represented by the symbol ${\Delta _i}H$ .

Complete step by step answer:
-Ionization enthalpy is defined as the amount of energy that is required by an isolated gaseous atom to lose an electron from its ground state to form a gaseous cation.
-It is also known as ionization potential.
-Ionization enthalpy is represented by ${\Delta _i}H$ .
-It increases from left to right as we go along the group and decreases down the period.
-The process of ionization enthalpy may be represented as follows:
${M_{(g)}} + {\Delta _i}H \to {M^ + }_{(g)} + {e^ - }_{(g)}$ .
${M_{(g)}}$ it represents the gaseous atom.
${M^ + }_{(g)}$ it represents the resultant gaseous cation.
-Ionization enthalpy is measured in electron volts per atom or kilojoules per mole.
Factors that govern ionization enthalpy is as follows:
-Nuclear charge
-Ionization enthalpy increases with the increase in nuclear charge.
As we go along a period from left to right ionization enthalpy increases with increased nuclear charge.
-Atomic size
-Ionization enthalpy decreases when the atomic size increases.
-Penetration effect
-Ionization enthalpy increases with the increase in the penetration effect of the electrons.
-The ionization enthalpies of the given elements is as follows:
Sulphur $(S)$ =$1000kJ/mol$ .
Phosphorous $(P)$ = $1012kJ/mol$ .
Arsenic $(As)$ = $946kJ/mol$ .
-Also as ionization enthalpies decreases as we go down the group because as the atomic number increases, the number of electrons also increases.

So, the correct answer is option (C) $As < S < P$.

Note:
Ionization energy and ionization enthalpy they both are two different things and not the same. Ionization enthalpy is the total sum of ionization energy and heat capacity. Ionization enthalpy increases as we go across the period from left to right.