Mammoth Memory

Copper atoms

To help us decide which way electricity flows, let's look at the structure of a copper atom which is used universally as an electrical carrier.

Atomic structure of a copper atom

In this neutral state of charge, the atom has the same amount of +ve protons as -ve electrons, i.e. 29.

But the outside shell only has one electron and is vulnerable to being removed. 

Outer shell of a copper atom

Electrons close to the nucleus are hard to remove while those in the outer ring require relatively little energy to be removed and become free electrons.

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