What is the electron configuration for Lithium?

Lithium has an atomic number of 3, which means it has three electrons. To determine its electron configuration, we start filling electrons according to the principles of the Aufbau principle, Hund's rule, and the Pauli exclusion principle.

The first two electrons go into the 1s orbital, which can hold a maximum of two electrons, resulting in the configuration 1s². The third electron then goes into the next available orbital, which is the 2s orbital. Therefore, the electron configuration for lithium can be expressed as 1s² 2s¹.

However, to provide a more compact notation, we can also use the noble gas shorthand. The nearest noble gas preceding lithium is helium (He), which has an electron configuration of 1s². Hence, the remaining electron configuration for lithium can be represented as [He] 2s¹, effectively indicating that after the configuration of helium, lithium has one additional electron in the 2s orbital.

This makes [He] 2s¹ the correct representation of lithium's electron configuration in shorthand form.