Question

In the ground state of cobalt atom (Z=27), number of unpaired electrons and the magnetic nature of cobalt are respectively.

• A. 2, diamagnetic
• B. 2, paramagnetic
• C. 3, diamagnetic
• D. 3, paramagnetic

Answer 1

The correct option is D 3, paramagnetic

Cobalt (Z=27)
As per pauli's exclusion principle the electronic configuration of cobalt is given as
$1s^2$$2s^2$$2p^6$$3s^2$$3p^6$$3d^7$​​​​​​​$4s^2$
or
$\left[Ar\right]3d^{7}4s^2$
Cobalt has 3 unpaired electron. Thus it is paramagnetic. The outermost subshell contains three electrons which are unpaired $3d^7$