Unit 3 Chemistry Test

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