Written by the Fiveable Content Team • Last updated September 2025
Verified for the 2026 exam
Verified for the 2026 exam•Written by the Fiveable Content Team • Last updated September 2025
Definition
The principle energy level of an atom refers to the major energy levels, or shells, where electrons reside. These are denoted by the numbers 1, 2, 3 and so on.
Related terms
Quantum Number: This is like the address for an electron in an atom. It defines the main energy level (floor), shape (apartment type) and orientation (room number).
Orbital: This is a region within an atom where there's a high probability to find an electron. It's like individual rooms in our apartment analogy.
These are electrons that occupy the outermost shell or principal quantum level of atoms. They're like people living on the top floor who have easy access to leave the building (react with other atoms).