Are all atoms the same size?

If gold is so dense, and helium is so gaseous...
18 June 2019


Atom cartoon



Is an atom always the same size? With something as dense as gold, or as gaseous as helium?


Chris - Sure. Well this sounds like one for Colm to answer. How big are atoms? Les is saying are they all the same size? Presumably not.

Colm - So Les all atoms of the same material are the same size but different items of different materials are different sizes. So for instance the single smallest item is hydrogen and a single hydrogen is about one twentieth of a nanometre across.

Chris - How big is a nanometre?

Colm - So a nanometre is one billionth of a metre. So, to give you an example, if you take a hair - so a hair is about 50,000 nanometres across - the distance between atoms in a typical material is about a quarter of a nanometre, and the size of a hydrogen atom is about one twentieth of a nanometre. Then, if you go up to something like gold, so gold is about one tenth of a nanometre at its outer radius. But all gold atoms are the same. All hydrogen atoms are the same.

Chris - So, in summary then, all atoms of a type - or one specific element - are the same size, but, because there are nearly a hundred and twenty different elements, there's 120 atoms of different sizes?

Colm - Right!


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