different atoms = different sizes

atoms have regular geometric shapes

All matter could be divided into smaller and smaller pieces
until a single invisible particle was reached (atom)

atoms are in constant motion

370-460 B.C.E

empty space between atoms

since the atoms of an element have identical properties such as mass and combine in constant ratios, every compound must have a fixed, definite composition.(Law of constant composition)

in chemical reactions, atoms join together or separate from
each other but are not destroyed

atoms of 2 or more elements can combine in constant ratios
to form new substances

atoms of different elements have different properties

all atoms of an element have identical properties

all matter is composed of invisible particles called atoms

1766-1844

proposes that an aton is a positive field with negative
embedded within it.

discovered that particles moving in the opposite direction to cathode rays deflect away from positive fields toward negative fields.

1897

predicted that all the alpha particles would travel through the
foil unaffected by the atoms of gold

large percent was unaffected

involved shooting particles(radioactive and positively
charged) through thin pieces of gold foil

small percent deflected at large angles

1911 an experiment was performed that tested the existing
atomic models.

atoms must contain a positively charged core(nucleus)
surrounded by empty spaces containing electrons

an atom is composed of a nucleus, containing protons and
neutrons, number of electrons = to the number of protons

demonstrated that atomic nuclei must contain heavy neutral
particles as well as positive particles

electrons within an atom can posses only certain discrete
energies

each energy levels has a fixed distance from the nucleus

developed new theory of atomic structure and communicated
this theory with a new model of the atom

Matter can changed between the 3 states: solid to liquid
(melting), liquid to gass ( evaporation), gas to
liquid(condensation), liquid to solid (freezing), solid to gas
(sublimation), and gas to solid (deposition)

The particle theory of matter: matter is composed of tiny objects
called particles, particles have space between them, particles are always in motion, and particles in a substance attract
each other.

Pure substances are either elements or compounds.
Elements can't be broken down by chemicals andcompounds are made by the formation of two or more
elements

Mixtures can be heterogeneous or homogeneous mixtures
look the same throughout, and the suspension is a mixture in
which tiny particles of a substance are held in.