Question

In the sixth period, the orbitals that are filled are ______.

Options

• 6s, 5f, 6d, 6p

• 6s, 5d, 5f, 6p

• 6s, 6p, 6d, 6f

• 6s, 4f, 5d, 6p

Answer 1

In the sixth period, the orbitals that are filled are 6s, 4f, 5d, 6p.

Explanation:

In period 6, the electrons first fill the 6s orbital. After 6s, the 4f orbitals are filled (these are the lanthanoid series). Once many 4f states are occupied, electrons begin to enter 5d orbitals. Finally, the 6p orbitals get filled. This order comes from the relative energies of these subshells (so 6s < 4f < 5d < 6p for filling in period 6).