| A | B |
|---|
| atom | The smallest unit of an element that retains the chemical properties of that element. |
| atomic theory | all matter is made up of individual particles called atoms |
| model | a simplified representation of a real object or a process that helps explain and understand that object or process |
| half-life | the amount of time that it takes for half of a radioactive sample to decay (break down) |
| electron | negatively-charged particle found outside of the nucleus |
| nucleus | the dense, positively charged center of an atom that is composed of protons and neutrons |
| proton | a positively charged particle found in the nucleus |
| neutron | subatomic particle that is found in the nucleus and has no charge. |
| atomic number | equal to the number of protons in the nucleus |
| isotope | atoms that have the same number of protons but different numbers of neutrons |
| mass number | te sum of the number of protons and neutrons in one atom |
| average atomic mass | the weighted average of the mass of isotopes of an element |
| radioactive isotope | any isotope that has an unstable nucleus and decays over time. |
| radioactive decay | the spontaneous disintegration of an atomic nucleus. This releases particles and radiation. |
| alpha decay | A nuclear reaction that releases an alpha particle from the nucleus. This decreases the atomic number by 2 and the atomic mass by 4 |
| alpha particle | particle consisting of two protons and two neutrons |
| beta decay | A nuclear reaction that releases an electron from the nucleus. This increases the atomic number by one. |
| beta particle | an electron |
| radiation | energy emitted by matter in the form of waves or particles |
| gamma ray | a form of high-energy radiation emitted during nuclear reactions. |
| fission | the splitting apart of an atomic nucleus into 2 smaller nuclei |
| fusion | the joining of 2 atomic nuclei to form a larger nucleus |
| parent isotope | A radioactive isotope that undergoes decay |
| daughter isotope | an isotope that is formed as a result of a nuclear reaction |
