* s subshell: The s subshell can hold a maximum of 2 electrons. The maximum number of unpaired electrons in an s subshell is 1. This is because the two electrons in an s subshell have opposite spins.
* p subshell: The p subshell can hold a maximum of 6 electrons. The maximum number of unpaired electrons in a p subshell is 3. This is because the three orbitals within the p subshell each hold one electron with the same spin before pairing up.
* d subshell: The d subshell can hold a maximum of 10 electrons. The maximum number of unpaired electrons in a d subshell is 5. Again, each of the five d orbitals can hold one electron with the same spin before pairing up.
* f subshell: The f subshell can hold a maximum of 14 electrons. The maximum number of unpaired electrons in an f subshell is 7. Each of the seven f orbitals can hold one electron with the same spin before pairing up.
Key Principle: Electrons will individually occupy each orbital within a subshell before pairing up in the same orbital. This is due to Hund's Rule, which minimizes electron-electron repulsion.
