Question

Energy required to ionise 1 mole of gaseous He
ion present in its ground state is
(1) 108.8 NA eV (2) 13.6 eV
(3) 54.4 eV
(4) 54.4 N eV​

Answer 1

Answer:

The correct answer is option (3).

Explanation:

Energy of the nth orbit of an atom:

$E_n=-13.6\times \frac{Z^2}{n^2} eV$

Where :

Z =atomic number

n = principle quantum number

Z for helium atom = 2

$E_1=-13.6\times \frac{2^2}{1^2} eV$

$E_{\infty}=-13.6\times \frac{2^2}{(\infty )^2} eV=0$

Ionization energy of He atom:

$I.E=E_{\inft}-E_1=0-(-13.6\times \frac{2^2}{1^2} eV)$

$I.E=54.4 eV$

The ionization energy of helium atom is 54.4 eV.