Question

The $1^{\text {st }}, 2^{\text {nd }}$, and the $3^{\text {rd }}$ ionization enthalpies, $I_{1}, I_{2}$, and $I_{3}$, of four atoms with atomic numbers $n, n+1$, $n+2$, and $n+3$, where $n < 10$, are tabulated below. What is the value of $n$ ?

Atomic number	Ionization Enthalpy (kJ/mol)
	$I_1$	$I_2$	$I_3$
n	1681	3374	6050
n + 1	2081	3952	6122
n + 2	496	4562	6910
n + 3	738	1451	7733

Answer 1

Since I.E. of $Na$ is $495.8 \,kJ \,mol ^{-1}$,
so $( n +2)$ should be $11$ .
$n +2=11$, So $n =9$