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proposed that all substances were made of small parts
Democritus (420 BC)
believed that all matter was either: earth, wind, or fire
Aristotle (420 BC)
proposed the first atomic theory
Dalton (1800's)
discovered electrons using cathode ray tubes experiment
JJ Thompson (1897)
discovered that atoms are mostly empty space with a small, dense region called a nucleus (used the gold foil experiment)
Ernest Rutherford (1911)
proposed that electrons orbit the nucleus at fixed energy levels.
introduced the planetary model.
Bohr (1913)
discovered the neuron
Chadwick (1932)
different number of neutrons and mass
isotopes
different number of electrons and charge
ions
compounds contain elements in exactly the same proportions by mass regardless of amount
Law of Definite Proportions
when different compounds are formed but contain the same 2 elements, different masses of 1 element combine with the same mass of the other element in a ratio of small whole numbers
Law of Multiple Proportions
neutrons have no charge
electrons have no mass
Subatomic Particles
name of element
number of protons
number of electrons in a neural atom (not ion)
Atomic Number
splitting a large atom into 2 smaller atoms
Nuclear Fission
absorbs neutrons
Control Rods
slows down some of the neutrons so they can't set off the next fission reaction
heavy water
used for nuclear power plants
Nuclear Fission
Element used in fission ractions
uranium
element used in fusion reactions
hydrogen
produces radioactive waste
Nuclear Fission
used in atomic bombs
fission
used in hydrogen bombs
fusion
occurs at temps 1 million plus degrees celcius
fusion
responsible for the energy of the sun and other stars
fusion
discovered radioactivity
Becquerel
discovered the first radioactive elements and came up with the name radioactive
curie
discovered that 1 large atom was splitting into 2 smaller atoms (fission)
Meitner
performed the first controlled chain reaction
Fermi
the most penetrating radiation
gamma rays
the joining of two small nuclei (atoms)
Nuclear Fusion
produces no radioactive waste
Fusion
the amount of time it takes for half of a radioactive isotope to decay a stable isotope
Half-Life
Excessive amounts of ________ make larger atoms more radioactive than smaller ones
Neutrons
a series of events where each event causes the next one
chain reaction
