| A | B |
|---|
| Chemical Symbol | A shorthand way to write the name of an element |
| Nucleus | The positively charged center of an atom |
| Electron | A negatively charged particle that orbits around the nucleus of an atom |
| Proton | A particle in the nucleus of an atom that has a positive charge |
| Neutron | A particle in the nucleus of an atom that has no electrical charge |
| Atomic Number | The number of protons in an atom's nucleus |
| Electron Cloud | The space where electrons most probably exist around the nucleus of an atom |
| Quarks | A very small particle of matter that makes up protons and neutrons |
| Mass Number | Total particles in an atom's nucleus |
| Isotopes | Atoms of the same element that have different numbers of neutrons |
| Periodic Table | A table of the elements, in order by increasing atomic mass, arranged in rows and columns to show their repeated properties |
| Group | One of the 18 vertical columns in the periodic table |
| Dot Diagram | A diagram of an atom, using the element symbol with dots to show the electrons in the outer energy level |
| Period | A horizontal row of elements in the periodic table; increasing from left to right is the number of electrons in the atoms' outer shell |
| Metals | An element usually having the following characteristics: shiny, ductile, and a good conductor of heat and electricity |
| Nonmetal | An element that usually lacks the characterics of a metal |
| Metalloid | An element having some properties of both a metal and a nonmetal |
| Atom | The smallest particle of an element |
| Element | A substance that cannot be broken down into simpler substances |
| Quarks | smaller particles that make up protons and nuetrons |
| Average Atomic Mass | The average mass of a mixture of an elements isotopes |
| Energy level | The possible energies that electrons in an atom can have |
| Valence electrons | Electrons that are found in the outer energy level |
| Orbital | A region of space around the nucleus where an electron is likely to be found |
| Ground State | When all electrons in an atom have the lowest possible energies |
