Question

Find the wavelength of radiation required to excite an electron in the ground level of $L{i}^{2+}$ (Z = 3) to the third energy level.

• A. $113.9\mathring{A}$
• B. $153\mathring{A}$
• C. $147.1\mathring{A}$
• D. $101.1\mathring{A}$

Answer 1

The correct option is A $113.9\mathring{A}$

$Li\to 3$ electrons
So, $Li\to 2,1$
But $L{i}^{2+}\to 1$ electrons
So, Transition will be from $n_1=1to{n}_2=3$

$\therefore \overline{\nu }=R{Z}^2[\frac{1}{n_1^2}-\frac{1}{n_2^2}]$
$\overline{\nu }=109677\times 3^2[\frac{1}{1^2}-\frac{1}{3^2}]$
$\overline{\nu }=8.77\times {10}^7{m}^{-1}$
Or $\lambda =\frac{1}{\overline{\nu }}=113.9\mathring{A}$