CHEM Chapter 3 Vocab

law of conservation of mass

mass is neither created nor destroyed during ordinary chemical reactions of physical changes

law of definite proportions

a chemical compound contains the same elements in exactly the same proportions by mass regardless of size or sample of source

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 2nd combine with a certain mass of the first is a ratio of small whole numbers

atom

the smallest chemical particle of an element that retains the chemical properties of that element

nuclear forces

short-range proton-neutron, proton-proton, and neutron-neutron forces hold nuclear particles together

atomic number

the number of protons in each atom of an element

isotope

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

general term for a specific isotope of an element

unified atomic mass unit (1 u)

exactly 1/12 the mass of a carbon-12 atom

average atomic mass

weighted average of the atomic masses of the naturally occurring isotopes of an element

mole (mol)

amount of substance that contains as many particles as there are atoms in exactly 12 g of carbon-12

Avogadro's number

6.022 141 79 x10^23 - the number of particles in exactly one mole of a pure substance

molar mass

the mass of one mole of a pure substance