Download Oct 27 day ten

Theories and
Structure of the Atom
Dalton’s Atomic Model (1805)
Dalton’s model of the atom was an indivisible
sphere of matter.
Dalton’s Contributions:
• Conservation of Mass (In any reaction, mass
before and after the reaction will be the
same)
• Elements can combine in different proportions
(Ex: H2O and H2)
Thompson’s Atomic Model (1897)
Thompson’s Contributions:
• J.J. Thompson discovered the idea of charge in
an atom
• His models placed the electrons throughout the
positively charged atom
• AKA raisin bun model
Rutherford’s Gold-Foil Experiment
Rutherford’s Atomic Model(1911)
Rutherford conducted an experiment where positively
charged alpha particles were fired at gold foil. His
observations included:


Most alpha particles passed straight through the foil
A few alpha particles bounced back
Rutherford’s contributions to the atomic
model
Since most of the alpha particles passed through
the foil:
1. Most of the atom is empty space
Since some of the alpha particles bounced back:
2. Part of the atom is very dense and positive.
(He called this the nucleus)
Rutherford’s Atomic Model (1911)
The nucleus is a
dense mass of
protons and
neutrons.
Electrons exist
outside the
nucleus.
Bohr’s Atomic Model (1913)
Bohr’s Contributions:
• Discovered that electrons exist in electron levels.
• Using hydrogen gas, he was able to show how
electrons have a certain amount of energy
and can “jump” from one level to the next.
Subatomic Particles
Particles
Charge
Mass
(amu)
Protons
1
Neutrons
1
Electrons
Negligible
(1/2000)
Location
History of the Atom Videos
http://www.youtube.com/watch?v=BhWgv0S
TLZs&feature=related
http://www.youtube.com/watch?v=WmmglV
Nl9OQ&feature=related
http://www.youtube.com/watch?v=FfY4R5m
kMY8&feature=related