# How do scientists count the exact number of electrons, protons, neutrons in the atom? [duplicate]

An atom is very small so it is probably difficult to focus exactly on a single atom. I wonder how scientists count the exact number of electrons, protons, neutrons in an atom of a certain element.

Could you explain it?

In other words, how do we know that for example, $\ce{^{19}_9F}$ has nine protons and ten neutrons and nine electrons?

• @inɒzɘmɒЯ.A.M I'm not sure if OP didn't maybe ask about single atoms not atoms in general? This meaning could stem from OP's misconception, but such question would be actually much more interesting. – Mithoron Aug 26 '15 at 14:04
• @Mith at first read, I didn't understand what they ask. I was gonna VTC, but then it struck me that they want to know how scientists find out how many protons are there in an atom. They could verify or correct me though. And yes, I think they're saying generally, but I figured an example would help. – M.A.R. Aug 26 '15 at 14:10