Electron Shells

Jemma Brown

What are Atoms made of?

Atoms are made up of a nucleus, containing protons and neutrons, and shells surrounding it which hold the electrons. An atom has the same amount of protons as electrons so when you draw an electron diagram, you can use the elements symbol to work the amount of electrons out.

Electron Diagrams

Electron Shells

In an atom, the electrons are on shells, which surround the nucleus. The first electron shell can only hold a maximum amount of 2 electrons. The second, third and so on shells can hold a maximum of 8 electrons.

Electronic Configuration

The electronic configuration of an atom shows someone the amount of electrons that an element has in each shell, without them having to draw an electron diagram. For example, fluorines electronic configuration is 2.7, so in its first shell there will be two electrons and in its second shell, there will be seven electrons. By looking at the group an element is in the periodic table, a person can work out the amount of electrons that an atom has in its outer shell.

Electronic Configurations of the first 20 elements

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In the periodic table, as you go across the periods, the amount of electrons in the outer shell of the atoms increases by one. As you go down the groups in the periodic table, all of the elements down the column have the same amount of electrons in their outer shells.