Question

If the ionisation potential of an atom is $20V$, its first excitation potential will be :-

• A. $5V$
• B. $10V$
• C. $15V$
• D. $20V$

Answer 1

Answer: (C)

$15V$

$E=13.6Z^2$

$⟹Z^2=\frac{E}{13.6}$

$⟹Z^2=\frac{20}{13.6}$

Excitation energy is given as $=-13.6\times [\frac{Z^2}{4}-\frac{Z^2}{1}]$ (equation $01$)

Putting $Z^2$ value in equation $01$

We get,

$⟹$ Excitation energy $=-13.6\times \frac{[\frac{20}{4}-\frac{20}{1}]}{13.6}$

$⟹$ Excitation energy $=15$ $V$