| A | B |
|---|
| atom | the smallest particle of a given type of matter |
| atomic theory | the idea that matter is made up of fundamental particles called atoms |
| law of definite proportions | principle that the elements that comprise a compound are always in a certain proportion by mass |
| hypothesis | prediction that can be tested to explain observations |
| experiment | set of controlled observations that test a hypothesis |
| theory | explanation based on many observations and supported by the results of many experiments |
| scientific method | a scientific approach used in scientific study (organized process by scientists) |
| scientific law | fact of nature that is observed so often that it is accepted as the truth |
| electron | negatively charged particle |
| proton | positively charged subatomic particles |
| isotope | any of 2 or more atoms of an element that are chemically alike but have different masses |
| neutron | subatomic particle with a mass equal to a proton but with no electrical charge |
| nucleus | small, dense, positively charged central core of an atom |
| atomic mass unit | 1/12 the mass of a carbon 12 atom |
| mass number | sum of neutrons and protons in the nucleus of an atom |
| atomic number | the number of protons in the nucleus of an atom of an element |
| electromagnetic spectrum | the whole range of electromagnetic radiation |
| emission spectrum | spectrum of light released from excited atoms of an element |
| energy level | regions of space in which electrons can move about the nucleus of an atom |
| electron cloud | space around the nucleus of an atom where the atom's electrons are found |
| valence electron | an electron in the outermost energy level of an atom |
| Lewis dot diagram | a diagram in which dots or other small symbols are placed around the chemical symbol of an element to illustrate the valence electrons |
