The Capacities of the Shells

Each shell has a maximum number of electrons that can be in it at any one time. This is called its capacity.

For this course, you need to know the capacities of the first four shells. They are as follows:

First Shell2
Second Shell8
Third Shell8
Fourth Shell18

Once a shell has reached its capacity, no more electrons can be added to it (in other words, no more electrons can orbit at that specific distance from the nucleus).


Flashcards help you memorise information quickly. Copy each question onto its own flashcard and then write the answer on the other side. Testing yourself on these regularly will enable you to learn much more quickly than just reading and making notes.


What is meant by ‘electron shell capacity’?


What are the capacities of the first four electron shells?


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