Question

Which statement best describes how electrons fill orbitals in the periodic table?
Electrons fill orbitals in order of their increasing energy from left to right.
Electrons fill orbitals in order of their increasing energy from right to left.
Elements fill orbitals in order of increasing energy from top to bottom in each group.
Elements fill orbitals in order of increasing energy from bottom to top in each group.

Answer 1

Electrons fill orbitals in order of their increasing energy from left to right.

This follows the aufbau principle — as you move left to right across the periodic table electrons are added one by one to the lowest‑energy available orbitals (with a few known exceptions like Cr and Cu).