| A | B |
|---|
| element | a substance that cannot be broken down into other substances by ordinary means |
| atom | smallest unit of an element that has all of the characteristics of that element |
| proton | positive particle in an atom |
| electron | negative particle in an atom |
| neutron | neutral particle in an atom |
| energy level | up to 7 located in the vast space of an atom outside of the nucleus |
| molecule | two or more atoms chemically combined |
| compound | substance that has been made up of two or more elements that have been chemically combined. |
| mixture | two or more substances mixed together |
| pure substance | has only one type of component |
| liquid | no definite shape, but has a definite volume |
| solid | definite shape and volume |
| gas | no definite shape or volume and will spread out to fill the entire space of its container |
| plasma | atoms are torn apart into charged particles making a gas-like state consisting of free electrons and ions |
| atomic number | number of protons in an atom’s nucleus |
| atomic mass | mass of an average atom of an element taking into account the percentages of its isotopes that exist naturally |
| density | how much matter is located within a given space |
| period | rows of the Periodic Table |
| physical property | can be observed without changing the identity of a substance |
| chemical property | characteristics of a substance that describe how the substance reacts with other substances |
| ion | atom or molecule that has lost or gained one or more electrons so that it has a positive or negative charge |
| isotope | forms of an element with the correct number of protons but a different number of neutrons (neutral charge) than indicated by the atomic mass |
| matter | anything having mass and volume |
| Homogeneous mixture | formed when the substances are evenly spread throughout the mixture, for instance sugar water |
| Heterogeneous mixture | formed when the substances are not evenly spread throughout the mixture, for instance soil. |
