atomic structure

Protons

positively charged and in the nucleus

Neutrons

Neutrally charged and in the nucleus

Electron

Negatively charged and on the outer ring of the Atom

Mass number

the sum of both the protons and nuetrons

Atomic number

the number of protons in an atom

Democritius

Atomos model. finely cut strips that couldn’t be cut anymore.

John Dalton

Law of definite preportion stated atoms are invisible, and that all atoms of the same elements have the same properties.

JJ thomson

proved that the atom was not indivisible but made of smaller parts. he found the electron using the cathode ray tube and made the plum pudding model.

Ernest Rutherford

using the gold foil experiment, he stated that alpha particles had the same composition as helium nucleus.

Niels bohr

he envisioned that electrons circled the nucleus like his planetary model. when electrons gain energy, they become in the excited state.