What is the final spin direction of the last electron in Argon?

The final spin direction of the last electron in argon, which has the atomic number 18, is typically +1/2. In its ground state electron configuration, argon has a full outer shell (3s² 3p⁶), meaning that the last electron occupies the 3p orbital. Electrons in orbitals are filled according to the Pauli exclusion principle and Hund's rule, but since all orbitals in the 3p subshell are fully occupied, the last electron's spin is conventionally considered to be +1/2.