Transcript History of the Atomic Model 2015

Finding Evidence of
Atoms
INPUT
Let’s Review…
• What is matter?
Anything that has mass
and takes up space
Energy (Light, sound, and
heat) are NOT matter.
• What is volume? Space matter takes up
• What is mass?
Amount of matter in an
object
The
The Atom
Atom
an amazing discovery
over centuries of
thought
Who was Democritus?
•
•
•
•
450 BC
A Greek philosopher who proposed the
idea that matter is made of tiny pieces that
could not be cut into smaller parts.
Called this atomos meaning “uncuttable”.
He used the idea of an apple being cut in half, then that
half being cut in half, and so on (sound familiar?).
Who was Dalton?
•
Early 1800s
•
English schoolteacher and scientist who did
many experiments on gases that led to a
new and more complete model of the atom.
•
Billiard Ball Model
What are the 5 principles of
Dalton’s Atomic Theory?
1. All matter is made up of atoms.
2. Atoms are neither created nor destroyed in
chemical reactions.
3. Atoms of different elements combine in wholenumber ratios.
4. Each element is made of a different type of atom.
5. The atoms of different elements have different
masses and properties.
What is Dalton’s Billiard Ball Model?
•
Atoms are smooth, hard spheres.
Who was JJ Thompson?
• 1897
• English scientist who discovered that atoms
contain negative charges.
• Cathode Ray experiment
– 1 positive & 1 negative metal plate
– Cathode ray bent towards positive plate
– A negative charge is present
• Plum Pudding Model
Plum Pudding Model
Plum Pudding Model
Who was Rutherford?
• 1911
• Thomson’s student discovered that Thomson
was not correct.
• Experimented with alpha particles and gold
sheet. Determined there must be a positive
charge inside the atom for alpha particles to
repel
• Discovered atoms are mostly empty space
with a positively charged nucleus due to
protons.
Who was Bohr?
• 1913
• Danish scientist proved Rutherford’s idea of
electrons being anywhere incorrect.
• Discovered that electrons have specific
amounts of energy, so they orbit the nucleus
at certain distances or energy levels.
• Onion model/Planetary model
Bohr’s Electron Energy Levels
• Electrons fill energy levels
• Start at closest to nucleus
1st: 2 eo 2nd: 8 eo 3rd: 18 eo 4th: 32 eo
Bohr Model
(with energy levels)
+ +
+ + +
+
Who was Schrodinger?
• 1926
• Electrons do not orbit the
nucleus like planets; they can
be anywhere in a cloudlike
region around the nucleus.
• Region where electrons are
likely to be found. Still related
to energy levels.
• Cloud Model
Who was Chadwick?
• 1932
• English scientist discovered the neutron in
the nucleus of the atom.
Radiation from a
Beryllium atom knocked
loose protons from
hydrogen atoms in a
paraffin wax target.
Proved it must be a
neutral particle about the
same mass as a proton.
Modern model:
At the center of the atom is a tiny
nucleus that contains most of the mass
of the atom in protons and neutrons.
Surrounding the nucleus are cloudlike
regions where electrons are found
moving very fast around the nucleus.
Modern Model of the Atom
OUTPUT
• Summary: Write one paragraph explaining
how the current atomic model came about.
Include contributions from Democritis,
Dalton, Thomson, Rutherford Bohr,
Schrodinger, and Chadwick. Be sure to
discuss the evolution of the different models.
5 sentence minimum.
Creating A Timeline
• Research the scientist and times
• Create a timeline to show the impact of
discovering the atomic model
• Be creative on your timeline-you don’t need
to follow a straight line format
Creating Timeline
• Your timeline must include the
following dates:
–1932
–1926
–1925
–1923
–1913
– 1905
– 1890’s
– Mid 1800’s
– 1803-1835
(early 1800’s)
– 450 B.C.
Creating Timeline
• Your timeline must include the
following people:
–Bohr
–Chadwick
–Dalton
–De Broglie
–Democritus
–Heinrich Hertz
– Pauli
– Rutherford
– Schroedinger
– Thomson
– Uhlenbeck &
Goudsmit
Creating Timeline
• Your timeline must include the following
experiments:
– Atomic Theory (5 parts)
– Electron clouds have distinct shapes
–
–
–
–
–
–
–
–
–
Electrons form wave like paths
Electrons have own quantum numbers
Electrons spin in either direction
Existence of electrons, Plum Pudding (PP) Model
Nucleus, Gold Foil Sheet
Philosopher who first coined the term atom
Photoelectric Effect
The Neutron
Using Hydrogen, proposed orbits in atom model
Creating Timeline
• Go farther by including some of
these scientist:
–
– Alchemists
–
– Albert Einstein
–
– Aristotle & fellow Greeks –
–
– Becquerel
–
– Coulomb
– Crookes
– the Curies
Geiger
Otto Hahn
Lavoisier
Lise Meitner
Robert Millikan
Murray Gell-Mann and
George Zweig
– Max Planck
– Glen T. Seaborg
Creating Timeline
• Add drawings to your timeline:
–Bohr’s Orbit Based or Planetary Model
–Dalton’s Solid Spherical Model
–Rutherford’s Nuclear Model
–JJ Thomson’s Plum Pudding Model
–Modern Electron Cloud/Orbital Model
How to Start
• Look up the people and see what
experiments and dates are listed
• Use the class website’s current unit
• Be warned …
• dates are approximate so you can change the dates on
your timeline-slightly change
• Looking for correct info and people