| A | B |
|---|
| atom | the smallest particle into which an element can be divided |
| atomic mass | the weighted average of the masses of all the naturally occurring isotopes of an element |
| atomic number | the number of protons in an atom |
| proton | positively charged particle in the nucleus of an atom |
| neutron | a particle with no charge (neutral) in the nucleus of an atom |
| electron | the negatively charged particle that orbits the nucleus in electron clouds |
| electron cloud | the regions inside an atom where electrons are likely to be found |
| John Dalton | He came up with an atomic theory & his model looked like a marble |
| John Thomson | He discovered the electron. His model was known as the "plum-pudding" model |
| nucleus | the center of an atom; contains protons & neutrons |
| Bohr model | This model showed that electrons move around the nucleus in definite paths |
| Ernest Rutherford | He discovered the atoms are mostly made up of empty space & that there was a nucleus |
| Niels Bohr | He is known for his Bohr model (where electrons orbit the nucleus in definite paths) |
| isotope | atoms that have the same number of protons but have different numbers of neutrons |
| model | a representation of an object or system |
