Question | Answer |
atomic mass unit (amu) | the measuring unit for atomic masses, based upon the mass of carbon |
atomic number | the number of protons in an atom, determines the element's identity |
atomic mass | the mass of an atom's protons plus its neutrons |
isotope | atoms of the same element that have different masses due to different numbers of neutrons |
molar mass | the mass of one mole of a substance; for example, one mole of carbon has a mass of 12.01 grams |
mole | a counting unit, 6.02 x 10 23, also known as Avagadro's number |
law of conservation of mass | mass is neither created nor destroyed during ordinary chemical reactions |
law of definite proportions | compounds contain the same elements in the same proportions by mass regardless of the size of the sample |
atom | the smallest unit of an element that maintains the properties of that element |
Democritus | ancinet Greek; idea of atoms being indivisible |
Aristotle | ancient Greek; idea that matter was continuous and that there were no such things as atoms |
Dalton | 1800's; created a five part atomic theory that is still in use today |
Rutherford | gold foil experiment determined that the nucleus of an atom is small, dense, and has a positive charge |
Thomson and Millikan | conducted experiements that determined that electrons are very small, negative, and found in all atoms |
proton | the positive part of an atom, found in the nucleus |
neutron | found in the nucleus of an atom, has no charge |
electron | negative part of an atom, found outside the nucleus |
nucleus | the center part of an atom where the protons and neutrons are located |