Ch. 3 Atoms: Building Blocks of Matter
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19 terms
Terms | Definitions |
|---|---|
 law of conservation of mass | States that matter can be neither destroyed nor created during ordinary chemical reactions or physical changes |
| law of definite proportions | states that chemical compounds contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound H2O |
| law of multiple proportions | if two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers C + O = CO C+O+O +CO2 |
| atom | the smallest particle of an element that retains the chemical properties of that element made up of a nucleus (protons and neutrons) and a region of electrons |
| nucleus | very small region located near the center of an atom |
| Electron, neutron, proton | Name the three subatomic particles in alphabetical order. |
| Thomson | concluded that electrons were prevalent in all atoms and had a large charge-to-mass ratio through experiments with cathode ray tubes |
| Millikan | measured the charge of an electron: 1/1837 the mass of a simplest type of hydrogen atom |
| nuclear forces | short range proton-neutron, proton-proton and neutron-neutron forces holding the nuclear particles together |
| atomic number | the number of protons in the nucleus of each atom of an element |
| isotopes | atoms of the same element with different masses U235/92 (mass number over atomic number) |
| mass number | total number of protons and neutrons in the nucleus of an isotope |
| nuclide | general term for any isotope of any element |
| atomic mass unit | exactly 1/12 the mass of a carbon-12 atom |
| average atomic mass | the weighted average of the atomic masses of naturally occurring isotopes of an element |
| mole | the amount of a substance that contains as many particles as there are atoms in exactly 12 g of carbon-12 |
| Avogadro's number | 6.022 x 10^23. The number of particles in exactly one mole of a pure substance |
| molar mass | the mass of one mole of a pure substance |
| chemical reaction | transformation of a substance or substances into one or more new substances |
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