Question

Write the electronic configuration of the $C{a}^{2+}$ in absence of Aufbau Principle.

• A. $1s^2,2s^{2}2p^6,3s^{2}3p^6$
• B. $1s^2,2s^{2}2p^6,3s^{2}3p^{3}4d^3$
• C. $1s^2,2s^{2}2p^6,3s^{2}3p^{5}4d^1$
• D. none of these

Answer 1

The correct option is A $1s^2,2s^{2}2p^6,3s^{2}3p^6$

The Aufbau rule states that in the ground
state of an atom, an electron enters the orbital with the lowest energy first
and subsequent electrons are fed in the order of increasing energies.
The word 'Aufbau' in German means 'building up'. Here, it refers to the filling up of orbitals with electrons.
So the correct configuration is $1s^2,2s^{2}2p^6,3s^{2}3p^6$
Hence option A is correct.