Question

The ionization energy of a hydrogen atom is 13.6 eV. The energy of the ground level in doubly ionized lithium is:

• A. -28.7 eV
• B. -54.4 eV
• C. -122.4 eV
• D. -13.6 eV

Answer 1

The correct option is C -122.4 eV

Bohr's model is used to solve this question,

According to this $E=-13.6\times \frac{Z^2}{n^2}$

So, in this the E is equal to energy of electron in $n^{th}$ shell of atom whose atomic number is Z

.

Now, same amount of energy with opposite sign must be given to electron in order to remove it. $I.E.=-13.6\times Z^{2}eV$ (As n=1)

Since for Lithium, Z=3

Therefore, you get $I.E.=-122.4eV$