Here is a question I was asked at a job interview not too long ago.
'Explain what atoms are in simple terms'
Despite a degree in physics, I made a dog's dinner of this & gave some rubbish about really really small things.
I was thinking about it recently and looked up a definition & found:
atom: the smallest particle of matter which can partake in chemical reactions.
Sounds straight forward. But then I thought, what is a chemical reaction? Isn't it just an interaction between atoms (and collections of atoms). But that's recursive isn't it?
Any suggestions for answers?