HISTORY OF THE ATOM REVIEW
Name________________________________
Period________Date____________________
1. _______________ was the ancient philosopher who first proposed the existence of atoms.
2. _______________ showed that matter is neither ___________________ nor _________________ in
chemical reactions, and is known as the “Father of Chemistry.”
3. _______________ created the first atomic theory. He thought that all atoms of an element are
identical, and that atoms of different elements are different from each other. His model of the atom is
represented below.
4. The Law of ___________________ _____________________ states that compounds always have
the same elements in the same ratio by mass.
5. _____________________ discovered the electron using a cathode ray tube. Current flows from the
___________ to the ___________. Because the beam was deflected toward a positively charged plate
(Letter C), the beam must have a ___________ charge. Because the beam was also affected by a
magnet (Letter A), cathode rays also have _______. This led to the __________ ____________ model
of the atom, shown below.
6. _______________________ is credited with discovering the nucleus of the atom, during his famous
__________________________experiment. He used a radioactive source to beam positively charged
_________ _________________ toward a very thin film of gold foil. Most of the particles
_______________________________________, but some were ____________ at various angles. From
this he concluded that most of the atom is ___________________, with a small _______________
charged nucleus in the center, and the electrons somewhere outside. His experimental results and newer
model of the atom are shown on the next page.
7. _____________ proposed that electrons moved in fixed orbits around the nucleus, like planets around
the sun - the ________ ___________ model.
(Left below)
8. In the modern model of the atom, the nucleus contains ___________ and ___________, with the
______________ outside in a cloud. (Right below)
9. ___________________ discovered radioactivity when pitchblende, an ore containing ______________,
exposed photographic film. Rutherford later showed three types of radiation, by exposing a beam of
radiation to electrical plates. An Alpha particle is the same as a ___________ ___________, has a
___________ charge, so is attracted to the ____________ plate. Write the symbol for an alpha particle
___________. A Beta particle is the same as an _____________, has a ___________ charge, and is
attracted to the ________ plate. The electron has less mass, so is deflected more. Gamma rays are pure
_________, have _____ charge, and thus are __________ by the electrical plates. Label the alpha
and beta particles and gamma rays in the drawing below.
_