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| periodic table | organizes all the known elementsw into a table based on atomic mass and structure and helps you predict how elements will react with one another; the periodic table organizes elements into columns and rows and shows an element's atomic number, symbol, name and atomic mass. |
| atomic number | The number of protons in an atom of an element; atoms of the same element always have the same number of protons; elements appear in the periodic table in order of increasing atomic number. |
| mass number | The total number of protons and neutrons in the nucleus of an atom. |
| isotopes | Atoms of the same elements with different numbers of neutrons; radioactive isotopes can be used to precisely determine levels of drugs, hormones, or viruses in a patient's body. |
| atomic mass | Average mass of an isotope of an element found in nature; atomic mass of an element is calculated by determining the average mass of a sample of that elements atoms. |
| Family of elements | The organizational group found on the periodic table in which the elements are listed in vertical columns based on physical and chemical properties. |
| alkali metals | Column 1 elements in the periodic table of elements. |
| alkaline earth metals | Column 2 of the periodic table of elements. |
| noble gases | a family of elements that all have eight valence electrons. |
| period | One of the 7 horizontal rows in the periodic table. |
| ion | A positively or negatively charged ion whose charge results from the loss or gain of electrons. |
| ionic bond | A type of bond formed by the attraction of positively and negatively charged ions. |
| molecule | Neutral particle that is formed when electrons are shared by atoms rather than being gained or lost. |
| covalent bond | Type of bond formed between atoms when they share electrons. |
| polar molecule | A molecule with unbalanced harges as a result of electrons being shared unequally. |
| nonpolar molecule | A molecule with balanced charges whose electrons are shared equally. |
