Electrons fill all orbitals before pairing up.

Electrons fill degenerate orbitals singly before pairing up.

Electrons occupy the lowest energy orbitals first without regard to pairing.

Electrons pair up in the same orbital before filling others.

The electron configuration of a transition metal is determined by filling the 3d orbitals after the 4s orbitals, following the atomic number.

Transition metals have a fixed electron configuration that does not change with atomic number.

The electron configuration is determined by filling the 4p orbitals before the 3d orbitals.

The electron configuration is based solely on the number of protons in the nucleus.

The electron configuration of transition metals is identical to that of main group elements.

Main group elements include d orbitals in their electron configuration.

The electron configuration of transition metals includes d orbitals, while main group elements primarily involve s and p orbitals.

Transition metals have only s orbitals in their configuration.

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4d⁶

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁷

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁴

lead (Pb)

tungsten (W)

iron (Fe)

chromium (Cr)

[Ar]4s² 3d¹⁰

[Ar]4s² 3d²

[Ar]3d⁵

[Ar]3d⁴

1

2

3

4

[Ar] 4s¹ 3d⁵

[Ar] 4s² 3d⁴

[Ar] 3d⁴

[Ar] 4s¹ 3d³

[Ar]4s² 3d⁶

[Ar]4s² 3d⁷

[Ar]4s² 3d⁵

[Ar]4s² 3d⁴