| A | B |
|---|
| atom | Smallest particle of an element that has all the properties of the element |
| Dalton | atomic theory |
| Rutherford | discovered the nucleus |
| Thompson | discovered the electron |
| Chadwick | discovered the neutron |
| proton | positively charged particle found in nucleus |
| neutron | neutral particle found in nucleus |
| electron | negatively charged particle found outside the nucleus |
| electron cloud | area where electrons can be found |
| Bohr | atomic model where electrons orbit the nucleus like planets around the sun |
| Modern model | atomic model where electrons behave both like waves and particles |
| orbitals | regions within energy levels that two electrons can occupy |
| valence electrons | electrons that occupy the outer most energy level |
| period | horizontal row of elements on the periodic table |
| group | vertical column of elements on the periodic table |
| ion | an atom that has lost or gained electrons |
| isotope | atoms of the same element with different numbers of neutrons |
| atomic number | number of protons in an atom of an element |
| mass number | the sum of protons and neutrons in the nucleus of an atom |
| atomic mass unit | it is equal to 1/12 the mass of a carbon-12 atom |
| average atomic mass | the weighted average of all the naturally occurring isotopes of an element |
| alkali metals | most active group of metals |
| alkaline earth metals | metals that have 2 valence electrons |
| halogens | most active group of nonmetals |
| nonmetals | all elements right of the zig zag line on the periodic table and hydrogen |
| metals | everything left of the zig zag line on the periodic table except hydrogen |
| semiconductors | group of elements with characteristics of both metals and nonmetals |
| transition metals | elements in groups 3-12 |
| lanthanide series | also called the rare earth elements |
| actinide series | all elements in this group are radioactive |
| noble gases | only nonreactive group of elements |
| mole | the SI base unit used to measure the amount of a substance, whose number of particles is the same as 12 g of carbon-12 |
| molar mass | the mass in grams of 1 mole of a substance |
| Avogadro's number | 6.022 X 10^23 |
| conversion factor | a ratio that is derived from the equality of two different units, used to convert from one unit to another |
| cation | positively charged ions |
| anion | negatively charged ions |
| s,p,d, and f | represents the different shapes of orbitals found in energy levels |
| periodicity | describes something that occurs over and over at regular intervals |
| Democritus | first person to use the term atom to describe the smallest particle of matter |
