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| 7912695263 | atomic number | the number of protons in the nucleus of an atom |  | 0 |
| 7912717907 | isotope | Atoms of the same element that have different numbers of neutrons | 1 | |
| 7912721023 | radioactive | A spontaneous process in which unstable nuclei lose energy by emitting radiation |  | 2 |
| 7912721024 | nuclear decay | When the number of protons and neutrons changes within and unstable nucleus. |  | 3 |
| 7912724269 | ion | An atom or group of atoms that has gained or lost one or more electrons, thus acquiring a charge. |  | 4 |
| 7912724270 | valence electrons | Electrons on the outermost energy level of an atom |  | 5 |
| 7912726624 | periodic table | a chart that organizes the elements by their chemical properties and increasing atomic number |  | 6 |
| 7912737469 | covalent bond | A chemical bond that involves sharing a pair of electrons between atoms in a molecule |  | 7 |
| 7912737470 | ionic bond | Formed when one or more electrons are transferred from one atom to another |  | 8 |
| 7912750435 | chemical formula | A combination of chemical symbols and numbers to represent a substance |  | 9 |
| 7912918702 | chemical bond | the force that holds two atoms together |  | 10 |
| 7912925494 | compound | A substance made up of atoms of two or more different elements joined by chemical bonds |  | 11 |
| 7912998486 | polar covalent bond | A covalent bond in which electrons are not shared equally |  | 12 |
| 7913006198 | molecule | two or more atoms held together by covalent bonds |  | 13 |
| 7913067108 | metallic bond | a bond formed by the attraction between positively charged metal ions and the electrons around them |  | 14 |
| 7913108844 | metals | Have a shiny or metallic luster, good conductors of heat and electricity. Tend to lose electrons when bonding. |  | 15 |
| 7913121988 | nonmetals | Elements that are poor conductors of heat and electric current. Most are gases, dull & brittle. They tend to gain electrons when bonding. |  | 16 |
| 7913224608 | alkali metals | Group 1 elements, which are very reactive metals. |  | 17 |
| 7913234220 | polyatomic ions | a charged group of covalently bonded atoms |  | 18 |
| 7913251320 | Alkali metals have _____ valence electrons. | 1 valence electron |  | 19 |
| 7913261058 | Halogens have _____ valence electrons. | 7 valence electrons | | 20 |
| 7913271905 | alkaline earth metals have ____ valence electrons. | 2 valence electrons | | 21 |
| 7913874333 | noble gases | Group 18: Nonreactive family of nonmetals; 8 valence electrons, full outer shell. All are gases at room temp. Normally do not bond with other elements. |  | 22 |
