| A | B |
|---|
| proton | A small, positively charged particle in the nucleus of the atom. |
| neutron | A small particle in the nucleus of the atom, with no electrical charge. |
| electron | A tiny negatively charged particle that moves around the nucleus of an atom. |
| nucleus | The central core of an atom containing protons and usually neutrons. |
| atomic number | The number of protons in the nucleus of an atom. |
| isotopes | An atom with the same number of protons and a different number of neutrons from other atoms of the same element. |
| mass number | The sum of protons and neutrons in the nucleus of an atom. |
| model | n science, a diagram, a mental picture, a mathematical statement, or an object that helps explain ideas about the natural world. |
| atomic mass | The average mass of all the isotopes of an element. |
| periodic table | A chart of the elements showing the repeating pattern of their properties. |
| chemical symbol | A one- or two-letter representation of an element. |
| period | A horizontal row of elements in the periodic table. |
| group | Elements in the same vertical column of the periodic table; also called family. |
| metal | A class of elements characterized by physical properties that include shininess, malleability, ductility, and conductivity. |
| malleable | A term used to describe material that can be pounded into shapes. |
| ductile | A term used to describe a material that can be pulled out into a long wire. |
| conductivity | The ability of an object to transfer heat or electricity to another object. |
| reactivity | The ease and speed with which an element combines, or reacts, with other elements and compounds. |
| corrosion | The gradual wearing away of a metal element due to a chemical reaction. |
| alkali metals | An element in Group 1 of the periodic table. |
| alkaline earth metals | An element in Group 2 of the periodic table. |
| transition metals | One of the elements in Groups 3 through 12 of the periodic table. |
| alloy | A mixture of two or more elements, one of which is a metal. |
| particle accelerators | A machine that moves atomic nuclei at higher and higher speeds until they crash into one another, sometimes forming heavier elements. |
