NOVA | What Makes An Element Reactive? - PBS

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Here are some of the main ideas students should take away from this video:

The location of electrons in an atom can be described as concentric shells around the nucleus of the atom.
The number of electrons in the outermost shell of an atom determines its reactivity.
Noble gases have low reactivity because they have full electron shells.
Halogens are highly reactive because they readily gain an electron to fill their outermost shell.
Alkali metals are highly reactive because they readily lose the single electron in their outermost shell.