What is He 2s1?

Answer 1

He 2s1 refers to a specific electronic configuration of a helium atom, where "He" stands for helium, and "2s1" indicates that there is one electron in the 2s orbital. In its ground state, helium has the electronic configuration of 1s², meaning both of its electrons occupy the 1s orbital. The notation "2s1" suggests that one electron has been promoted to the 2s orbital, which can occur in excited states. This configuration is important in understanding helium's chemical properties and behavior in various physical contexts.