| Definition | Term |
| Atoms with the same number of protons and different numbers of neutrons | |
| A material that can be hammered or rolled into flat sheets or other shapes is said to be _____ | |
| Positively charged particles in an atom | |
| Scientist who discovered electrons | |
| True or false: Most nonmetals are poor conductors of electric current and heat. | |
| Region in the center of an atom | |
| Rows in the periodic table | |
| Describes how shiny a metal is | |
| Average mass of all the isotopes of an element | |
| Substance that can conduct electric current under some conditions but not under other conditions | |
| Columns in the periodic table | |
| Scientist who thought that the atom was just a round ball that couldn't be broken into smaller pieces | |
| True or false: The number of protons always stays the same as the number of electrons in an atom. | |
| The number of protons in the nucleus of an atom | |
| Scientist who discovered that the atom had a positively charged nucleus | |
| Particle in the atom with no charge | |
| These have some properties of metals and some properties of nonmetals | |
| Name of the modern model of the atom | |
| Scientist who developed the first periodic table of elements (last name only) | |