Atomic Structure

An atom is the smallest unit of an element. An atom is made of neutrons, protons and electons. Protons are the positively charged. Electrons are negatively charged. And Neutrons don't have any charge.
Around 460 B.C., a Greek Philosopher, Democritus, Develop the idea of atoms. His question was: if you break a piece of matter in half, and then break it in half again, how many breaks will you have before you can break no further? So he thought it ended at some point, a smallest possible bit of matter. Which he called these basic matter particles, or atoms.

In 1897, a English physicist J.J. Thomson discover the electron so he thought that matter must have a positive charge. his model looked like raisins stuck on a lump of pudding.



Virtully all the mass of an atom is in the nucleus, because the electrons weigh so little.

The number of protons = Atomic Number of the atom

The number of protons + number of neutrons = Mass Number of then atom