Question

Ionisation energy of $Li$ (Lithium) atom in ground state is $5.4\, eV$. Binding energy of an electron in $Li^+$ ion in ground state is $75.6\, eV$. Energy required to remove all three electrons of Lithium (Li) atom is

• A. $81.0\,eV$
• B. $135.4\,eV$
• C. $203.4\,eV$
• D. $156.6\,eV$

Answer 1

Answer: (D)

$156.6\,eV$

Answer 2

Ionisation energy is $E_1 = 5.4\,ev$ Binding energy in ground $E_2=75.6\,ev$ Total energy required to remove all three electron $E=E_1 +2E_2$ $=5.4+2\times75.6$ $=156.6\,ev$