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14 terms

ch.3 Atoms: The building blocks of matter

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law of conservation of mass
mass is neither created nor destroyed during ordinary chemical reactions or physical changes
law of definite proportions
hemical compound contains the same lements in exactly the same proportions by mass regardless of the size of the sample or source of the compound
law of multiple proportions
if 2 or more differents compounds are composed of the same 2 elements, then the ratio of the masses of the 2nd element combined with a certain mass of the 1st element is always ratio of small whole numbers
atom
smallest particle of an element that retains the chemical properties of that element
nuclear forces
short range proton-neutron, proton-proton, and neutron-proton, and neutron-neutron forces hold the nuclear particles together
atomic number
number of protons of each atom of that element
isotopes
atoms of the same element that have different masses
mass number
total number of protons and neutrons that make up the nucleus of an isotope
nuclide
specific isotope of an element
atomic mass unit
1/12 the mass of carbon-12 atom
average atomic unit
weighted average of the atomic masses of the naturally occuring isotopes of an element
mole
amount of substance that contains as many particles as there are atoms in exactly 12 g of carbon-12
avogadro's number
6.002 1415x10*23 number of particles in exactly 1 mole of a pure substance
molar mass
mass of 1 mole pure substance