| A | B |
|---|
| atom | the smallest particles of matter |
| atomic theory | the idea that matter is made up of fundamental particles called atoms |
| law of conservation of matter | matter is neither created nor destroyed |
| law of definite proportions | the principle that the elements that make up a compound are always in a certain proportion by mass |
| hypothesis | a testable prediction to explain theri observations |
| theory | an explanation based on many observations and supported by the results of many experiments |
| scientific law | a fact of nature that is observed so often that it becomes accepted as the truth |
| electrons | invisble, negatively charged subatomic particles |
| protons | positively charged subatomic particles |
| isotopes | atoms that are chemically alike but differ in mass |
| neutron | a neutral subatomic particle |
| nucleus | the small dense, positively charged core of an atom |
| atomic number | the number of protons in an element |
| mass number | sum of protons and neutrons of an atomn |
