All matter is formed from indivisible atoms.
a particle that cannot be divided or destroyed
A small core of nucleons (protons and neutrons) surrounded by an attenuated cloud of electrons.
A Carbon atom joined to an Oxygen atom by a double bond.
He didn't "discover" anything. He took a wild guess about what very small pieces of matter were like based on really no tangible evidence whatsoever and happened to be approximately correct if you're not too terribly picky about the details.
The nucleus of an atom is the densest part of an atom. It contains the protons and neutrons of an atom.
a particle that cannot be divided or destroyed
Tapir
Agouti
Musk Ox
Baboon
Impala
Spotted Owl
Gnu
Prairie Chicken
Sea Turtle
gibbon
Walkingstick