In the electron configuration notation, the number before the letter represents the (a)   .

The maximum number of electrons in the second energy level is (a)   .

The electron configuration for oxygen is (a)   .

The (a)   principle states that electrons occupy the lowest energy orbitals first.

In the electron configuration 1s² 2s² 2p⁶, the 'p' indicates the type of (a)   .

The Aufbau principle is used to determine the order of filling (a)   in an atom.

The electron configuration for a sodium atom (Na) is (a)   .

The term 'valence electrons' refers to the electrons in the (a)   shell.

The Pauli Exclusion Principle states that no two electrons in an atom can have the same (a)   .