| A | B |
|---|
| atomic number | the number of protons in an atom |
| isotopes | atoms of the same element that have different numbers of neutrons |
| mass number | the sum of the neutrons and protons in the nucleus of an atom |
| radioactive decay | releasing energy and particles from the nucleus |
| transmutation | the change of one element into another through radioactive decay |
| half-life | time it takes for half the atoms of a radioactive isotope to decay |
| element | substance that cannot be broken down into simpler substances |
| electron | negatively charged particles that exists in an electron cloud formation around an atom's nucleus |
| proton | positively charged particle in the nucleus of an atom |
| neutron | electrically neutral particle that has the same mass as a proton and is found in an atom's nucleus |
| electron cloud | region surrounding the nucleus of an atom, where electrons are most likely to be found |
