Electron Configuration Generator

What is Electron Configuration?

Electron configuration describes the distribution of electrons among the orbitals of an atom. It follows three key principles:

Aufbau Principle

Electrons fill orbitals starting from the lowest energy level. The filling order is:

1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p → 6s → 4f → 5d → 6p → 7s → 5f → 6d → 7p

Pauli Exclusion Principle

No two electrons in an atom can have the same set of four quantum numbers. Each orbital can hold a maximum of 2 electrons with opposite spins.

Hund's Rule

Electrons occupy degenerate orbitals (orbitals of the same energy) singly before pairing up. Each single electron has the same spin direction.

Subshell Capacities

• s subshell: 1 orbital, holds 2 electrons
• p subshell: 3 orbitals, holds 6 electrons
• d subshell: 5 orbitals, holds 10 electrons
• f subshell: 7 orbitals, holds 14 electrons

Noble Gas Shorthand

The noble gas shorthand replaces the inner electron configuration with the symbol of the preceding noble gas in brackets. For example, sodium (Na) is written as [Ne] 3s¹ instead of 1s² 2s² 2p⁶ 3s¹.

Notable Exceptions

Some elements have configurations that differ from what the Aufbau principle predicts, due to the extra stability of half-filled and fully-filled subshells:

• Chromium (Cr): [Ar] 3d⁵ 4s¹ (not 3d⁴ 4s²)
• Copper (Cu): [Ar] 3d¹⁰ 4s¹ (not 3d⁹ 4s²)
• Silver (Ag): [Kr] 4d¹⁰ 5s¹ (not 4d⁹ 5s²)
• Gold (Au): [Xe] 4f¹⁴ 5d¹⁰ 6s¹ (not 5d⁹ 6s²)