| A | B |
|---|
| actinides | elements 90-103 (after actinium) |
| alkali metals | any element in group 1A of the periodic table |
| alkaline earth metals | any element in group 2A of the periodic table |
| atom | the smallest particle of an element that retains its identity in a chemical reaction |
| atomic number | the number of protons in the nucleus of an atom |
| atomic radius | one half the distance between the nuclei of two adjacenet atoms of the same element |
| Aufbau principle | electrons enter orbitals of lowest energy first |
| charge | due to an imbalance of protons and electrons in an ion |
| diagonal rule | chart that illustrates the order of sublevel filling according to the Aufbau Principle |
| electron | negatively charged sub-atomic particle |
| electron configuration | the arrangement of the electrons of an atom in its ground state |
| electronegativity | the tendency of an atom to attract an electron to itself when chemically combined with another atom |
| energy sublevel | division of principle energy levels; can be s, p, d, or f |
| family | elements (in the same column) that have similar chemical and physical properties |
| group | a vertical column on the periodic table |
| halogens | a nonmetal in Group 7A on the periodic table |
| Hund's rule | One electron will occupy each orbital of the same energy, before a second electron is added to each orbital |
| inner transition metals | an element in the lanthanide or actinide series on the periodic table |
| ion | an atom or group of atoms that have a positive or negative charge |
| ionization energy | energy required to remove an electron from an atom when it is in the gaseous state |
| isotope | atoms of the same element that have the same number of protons, but a different number of neutrons |
| lanthanides | elements 58-71 (after lanthanum) |
| mass number | the sum of the protons and neutrons in the nucleus of an atom |
| metals | one class of elements that are good conductors of heat and electricity; found to the left of "the step" on the periodic table |
| metalloids | an element that tends to have properties that are similar to those of metals AND nonmetals |
| neutron | a subatomic particle with no charge; found in the nucleus of an atom |
| noble gases | Group 8A on the periodic table; a group of elements that do not react with other elements due to complete s and p sublevels |
| nonmetals | one class of elements that are poor conductors of heat and electricity; found to the right of "the step" on the periodic table |
| nuclear charge | pull of the protons (in the nucleus) on the electrons in an atom |
| nucleus | the tiny, dense, central part of an atom, composed of protons and neutrons |
| orbital | division of sublevels in which electrons are found |
| Pauli exclusion principle | no more than 2 electrons, of opposite spin, may occupy the same orbital |
| period | a horizontal row on the periodic table |
| principle energy level | average distance an electron is from the nucleus of an atom |
| proton | a positively charged sub atomic particle that can be found in the nucleus of an atom |
| representative elements | an element that belongs to any of the "A groups" on the periodic table |
| semi-metals | an element that tends to have properties of that are similar to those of metals AND nonmetals |
| shielding effect | inner electrons protect valance electrons from nuclear pull |
| spectroscope | an instrument used for producing and observing a spectrum of light |
| valance electrons | an electron in the highest occupied energy level of an atom |
| atomic weight (atomic mass) | the weighted average of the masses of the isotopes of an element |
