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How many electrons fit in each shell around an atom?

The maximum number of electrons that can occupy a specific energy level can be found using the following formula:

Electron Capacity = 2n2

The variable n represents the Principal Quantum Number, the number of the energy level in question.

Energy Level
(Principal Quantum Number)
Shell LetterElectron Capacity
1K2
2L8
3M18
4N32
5O50
6P72

Keep in mind that an energy level need not be completely filled before electrons begin to fill the next level. You should always use the Periodic Table of Elements to check an element's electron configuration table if you need to know exactly how many electrons are in each level.

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