Question

The energy of an electron in the first orbit of the hydrogen atom is $-2.18\times 10^{- 18}\,J/atom$ . What is the third ionisation energy of $Li^{2 +}$ ion?

• A. $8.72\times 10^{- 18}J$
• B. $4.36\times 10^{- 18}J$
• C. $+19.62\times 10^{- 18}J$
• D. $6.54\times 10^{- 18}J$

Answer 1

Answer: (C)

IlI. Ionisation energy of $Li ^{+2}$
$=-\frac{ z ^{2}}{ n ^{2}} E _{1} H \quad( z =3, \quad n =1)$
$=-\frac{ z ^{2} \times-2.18 \times 10^{-18}}{ n ^{2}} J /$ species
$=--9 \times 2.18 \times 10^{-18}$
$=19.62 \times 10^{-18} J$