Shell Model of Helium

Physical Environment > Shell Model of Helium

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2. Now imagine we add a second electron to this atom. This shares the space with the first electron.
These two electrons now fill the space around the nucleus, so that no other electrons can enter it. (The reason why this happens is beyond the scope of this journal). The atom now behaves as if it had a hard outer shell. It will not interact with other atoms. Atoms like this are called noble gases.
The atom is now like helium.