law of definite proportions
a given compound always contains exactly the same proportion of elements by mass
Conversation of mass
When matter changes the total mads is the same as total mass of reactants
atomic mass
Number of protons and neutrons
atomic number
of protons
mass number
the sum of the number of neutrons and protons in an atomic nucleus
Isotope
Atoms of the same element have different numbers of neutrons
Ions
Mean atom has lost or gained electrons
Democritus
Greek philosopher said all matter is made of tiny particles called "atomos" or atoms
Atomos
greek word for atom- means not able to be divided
John Dolton
developed the atomic theory
Atomic Theory (Dalton)
All matter is made of atoms
2.(not true) atoms are indestructible and indivisible
compounds are combinations of different atoms
(Not true)
JJ Thomson
discovered electron with a cathode ray tube
Made plum pudding model
Ernst Rutherford
A discovered nucleus that most mass is in the nucleus
Did the gold foil experiment
Neils Bohr
-said that electrons are in energy levels, discovered Energy levels with hydrogen gas
Used planetary models
Robert Millikan
Oil drop experiment
Discovered the charge of an electron
Sir James Chadwick
discovered the neutron
Explains why electrons move
Changed model
The nuclear notation
shows the atom's symbol, mass number, and atomic number
A
mass number A=Z+N
Z
atomic number (number of protons)
X
chemical symbol for the element
N
neutron number
hyphen notation
the mass number is written with a hyphen after the name of the element
Law of Multiple Proportions
Whenever two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers.
Things we know about electrons
-electrons farther from the nucleus have higher energy
further levels can hold 2n2 electrons n=energy levels
Proton symbol
p+
Neutron symbol
n0
electron symbol
e^-
what holds the nucleus together
strong nuclear force
energy levels
The first energy level can hold 2 electrons
The second energy level can hold 8 electrons
average atomic mass
the weighted average of the atomic masses of the naturally occurring isotopes of an element
average atomic mass formula
(Percent to decimal)(mass) + (percent to decimal)(mass)
weighted averages
(abundance 1) * (mass 1) + (abundance 2) * (mass 2) + (abundance 3) * (mass 3)
Wener Heisenberg
Heisenberg Uncertainty Principle - Cannot know the speed and location of an electron at the same time.
Erwin Schrodinger
In 1926 developed the basic mathematical equation for quantum mechanics
nucleus size
small but massive(dense)
electron size
small and spread out
mole
the SI base unit used to measure the amount of a substance
molar mass
the mass of one mole of a pure substance
strong nuclear force
the powerful attractive force that binds protons and neutrons together in the nucleus