Question

The excepted ground state configuration for $Cu$ is:
$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^9$
The actual configuration is:
$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}3d^{10}$
Why is the true electron configuration different?

• A. The actual configuration increases stability by filling one energy level before moving on to the next. Disturbing the electrons this way gives a paramagnetic formation.
• B. The actual configuration decreases stability by filling a $3d$ sublevel before a $4s$ sublevel. Distributing the electrons in this way gives a diamagnetic formation.
• C. The actual configuration increases stability by creating a full d sublevel. Distributing the electrons in this way gives a diamagnetic formation.
• D. The actual configuration decreases stability by creating a half filled s sublevel. Distributing the electrons in this way is called a paramagnetic formation.

Answer 1

The correct option is C The actual configuration increases stability by creating a full d sublevel. Distributing the electrons in this way gives a diamagnetic formation.

In actual configuration the $3d$ sub shell is completely filled as a result, the atom gains extra stability due to diamagnetic formation. Thus the correct reason is given in option C. Hence answer is option C.