| A | B |
|---|
| atom | smallest stable particle of matter |
| atomic number | number of protons in the nucleus of atom of an element |
| atomic theory | idea that matter is made up of fundamental particles called atoms |
| electromagnetic spectrum | whole range of electromagnetic radiation |
| electron | negatively charged particle |
| electron cloud | space about atom's nucleus where it's electrons are found |
| 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 |
| hypothesis | prediction that can be tested to explain observations |
| isotope | any of two or more atoms of an element that are chemically alike but have different masses. |
| law of definite proportions | principle stating that elements that comprise a compound are always in a certain proportion by mass. |
| Lewis dot diagram | Diagram where dots or other small symbols are placed around the chemical symbol of an element to illustrate the valence electrons |
| mass number | sum of the neutrons and protons in the nucleus of an atom |
| 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 |
| proton | positively charged subatomic particle |
| scientific law | fact of nature that is observed so oftenthat it is accepted as the truth |
| theory | explanation based on many observations and supported by the results of many experiments |
| valence electron | electron in the outermost energy level of an atom |
