Transcript Atomic Models:

Atomic Models:
Democritus. All things were
made of atoms and they were
.
indivisible.
1800 AD Dalton
Atoms can not be broken into
smaller pieces – atoms are like a
.
solid marble .
All atoms of
.
an element were identical .
1900’s Rutherford’s gold foil experiment
• http://www.shsu.edu/%7Echm_tgc/sounds/p
ushmovies/l2ruther.gif - source of animation
History of Atomic Models
• Rutherford- all mass of an atom was in the
center- the nucleus- discovered by gold foil
experiment
– Electrons surround nucleus and travel in orbits like
planets around the sun
– Problem: did not distinguish protons & neutrons
and electrons do not actually move in the way he
thought
– http://www.chemsoc.org/timeline/pages/1911.html
Rutherford and Bohr
• Bohr-electrons travel in a fixed orbit around the
nucleus
– Problem: electrons are actually in regions or clouds around
the nucleus
• Difference between Bohr and Rutherford:
– Rutherford said electrons travel in orbits like planetsproblem- electrons also emit energy and should spiral
closer to the nucleus
– Bohr- only certain orbits are possible – they gain and lose
energy as they move from one orbital to another
• Distiguished between protons and neutron while Rutherford did
not
Current atomic model
• Electron Cloud Model- nucleus with protons
and neutrons in the center
– Electrons in clouds around the nucleus- very large
area compared to the nucleus
– Electrons move too fast to find exact location at
any one time
– Atoms are mostly empty space!
http://www.teachersdomain.org/resource/phy03.
sci.phys.matter.atoms/
Atoms
• Even protons, and neutrons are made up of
smaller particles- quarks
• Quarks- smallest particles- make up protons,
neutrons, and electrons- 6 types
– up, down, top, bottom, strange and charm
• To study quarks- You have to accelerate
charged particles to high speeds and cause
them to collide with protons, breaking the
proton
For now let’s stick to protons, neutrons, & electrons