# Which of the following options does not represent ground state electronic configuration of an atom? Option 1) $1s^{2}2s^{2}2p^{6}3s^{3}3p^{6}3d^{8}4s^{2}$ Option 2) $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{1}$ Option 3) $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{5}4s^{1}$ Option 4) $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{9}4s^{2}$

V Vakul

Aufbau Principle -

In the ground state of the atoms, the orbitals are filled in order of their increasing energies.

- wherein

Electrons fill the orbitals in the order of increasing energy. By t hat rule 3d orbit should fill up before 4s.

Option 1)

$1s^{2}2s^{2}2p^{6}3s^{3}3p^{6}3d^{8}4s^{2}$

Incorrect

Option 2)

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{1}$

Incorrect

Option 3)

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{5}4s^{1}$

Incorrect

Option 4)

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{9}4s^{2}$

Correct

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