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.

Explanation:

To determine the correct statement about electron filling in orbitals of the periodic table, we analyze each option:

1. Option 1: Electrons fill orbitals in order of their increasing energy from left to right.

The Aufbau principle states that electrons occupy orbitals starting from the lowest energy level. As we move from left to right across a period, the atomic number increases, and electrons fill orbitals (e.g., \( s \), \( p \)) in order of increasing energy. This aligns with the periodic trend of electron configuration.

1. Option 2: Electrons fill orbitals in order of their increasing energy from right to left.

This is incorrect. Moving right to left would imply decreasing atomic number and energy, which contradicts the Aufbau principle.

1. Option 3: Elements fill orbitals in order of increasing energy from top to bottom in each group.

Within a group (vertical column), elements have the same valence electron configuration. Moving top to bottom, energy levels (shells) increase (e.g., \( n = 2 \) to \( n = 3 \)), but the order of filling is determined by energy, not group direction. This statement misinterprets the trend.

1. Option 4: Elements fill orbitals in order of increasing energy from bottom to top in each group.

Moving bottom to top in a group decreases the principal quantum number (\( n \)), which corresponds to lower energy. This is the reverse of how electrons fill (they fill from lower to higher energy, not bottom to top in groups).

Answer:

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