Question

With which of the following electronic configuration of an atom has the lowest ionisation enthalpy?

• A. $1s^2 , 2s^2, 2p^5$
• B. $1s^2,2s^2 2p^3$
• C. $1s^2,2s^2 2p^6,3s^1$
• D. $1s^2 , 2s^2 2p^6$

Answer 1

Answer: (C)

The electronic configuration $1s^2,2s^2 2p^6,3s^1$ shows lowest ionisation energy because this configuration is unstable due to the presence of one electron in s-orbital. Hence, less energy is required to remove the electron.