| A | B |
|---|
| alpha particle | small positively charged particles used by Rutherford when testing the structure of the atom |
| atomic number | defined as the number of protons in an atom |
| atomic mass | average of the mass numbers for the common isotopes of an element |
| catalyst | a substance which speeds up a chemical reaction but does not take part in it |
| Chadwick | scientist who discovered the neutron |
| Crookes Tube Experiment | experiment which showed the existence and negative charge of an electron |
| extrapolate | to estimate a number outside or beyond numbers on a graph |
| Gold Foil Experiment | experiment which showed the existence of a nucleus |
| half life | time required for one half the atoms of a radioactive element to decay |
| interpolate | to estimate between two known numbers on a graph |
| isotopes | atoms of the same element with different number of neutrons |
| Law of Conservation of Mass | states that mass can not be created or destroyed in a chemical reaction |
| mass number | the total number of protons and neutrons in an atom |
| neutron | the neutral subatomic particle . . . found inside the nucleus |
| nucleus | the dense, positive center of atoms . . . containing protons and neutrons |
| proton | positively charged subatomic particle . . . found inside the nucleus |
| radioactive decay | spontaneous breaking apart of a nucleus to form a stable atom |
| Rutherford | scientist who discovered the nucleus and proton |
| Thomson | scientist with the "plum pudding model" for the atom and discovered the electron |
| trace element | an element found in very small amounts in the human body |
| Dalton | scientist who believed atoms were solid balls and were unique for each element |
| electron | the negative subatomic particle . . . found outside the nucleus |
| Law of Constant Composition | states that a compound always has the same relative number and type of atoms |
