The Law of Conservation of Mass
mass is neither created nor destroyed during ordinary chemical reactions or physical changes
The Law of Definite Proportions
a chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound
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
Atom
the smallest particle of an element that retains the chemical properties of that element
Protons
positively charged particles
Neutrons
neutral particles
Electrons
negatively charged particles
they occupy the large region around the nucleus
Subatomic particles
protons, neutrons, and electrons
Nucleus
very small region located at the center of an atom
Alpha particles
positively charged particles with about four times the mass of a hydrogen atom
cathode-ray tubes (p.72)
Plum Pudding Model (p.73)
Rutherford etc.
hyphen notation (p.79)
nuclear symbol (p.79)
...
Nuclear forces
short-range proton-neutron, proton-proton, and neutron-neutron forces hold the nuclear particles together
Atomic Number
(Z) the number of protons of each atom of that element
Mole (mol)
the amount of a substance that contains as many particles as there are atoms in exactly 12 g of carbon-12
Isotopes
atoms of the same elements that have different masses. they have the same number of protons and electrons but different number of neutrons. they have different masses but they do not differ significantly in their chemical behavior.
protium
deuterium
tritium
three types of hydrogen atoms are known... (p.78)
Mass Number
the total number of protons and neutrons that make up the nucleus of an isotope
Nuclide
a general term for a specific isotope of an element
atomic mass unit (amu) (p.80)
...
Average atomic mass
weighted average of the atomic masses of the naturally occurring isotopes of an element (usually rounded to two decimal places before it is used in a calculation)
Avogadro's number
the number of particles in exactly one mole of a pure substance
6.022 x 10��
Molar Mass
the mass of one mole of a pure substance
units = g/mol