Transcript Chemistry 11 Early Models of the Atom

Chemistry 11
Early Models of the Atom
A Short History of Investigating Matter
Around 450 BC, Empedocles suggested that all
matter was made of 4 elements:
Earth, Air,
Water
and
Fire
I think this pretty
well covers
everything!
Empedocles
LOOK OUT SONNY!
I could break you right
down into atoms! (But
nothing smaller!)
In 500 BC , Democritus proposed that all matter
could be broken down into atoms. These atoms
could not be broken down farther.
Sorry Democritus!
I am the famous
Aristotle and I
don’t like your
“atom” idea. I
disagree and
people are going to
believe me for
2000 years. So
take THAT!
Guys, if we
could just
change this lead
and copper into
GOLD, we’ll be
filthy rich! We
can drive
around in brand
new SUV’s
listening to
SIRIUS satellite
Some Alchemists
In the Middle Ages scholars searched for
the “Philosopher’s Stone” which would
help them change Lead or Copper into
GOLD!
Much later, Harry
Potter became
involved in the
same search?????
In 1669, Hennig Brandt
distilled some urine. He
found a pasty white solid
which glowed in the
dark!
He had actually
discovered a new
element “phosphorus”.
He didn’t think about it
being a new element
because he still believed
there were only the four.
Hey! This came from
pee !!!
NO! I am NOT
cutting my hair!!
I also disagree with
Aristotle! I think there
are WAY more than
four elements!
Sir Robert Boyle
Robert Boyle (1627-1691), an English scientist
thought air was a mixture rather than an
element. He also thought Brandt’s white paste
and gold were elements.
In 1661, Boyle published a
book called “The Sceptical
Chymist”
HEY! Maybe I can
get on the OPRAH
show to help sell my
book!
In the late 1700’s the Scientific Revolution was
taking place. Many old ideas were being
challenged!
“You say you want a
revolution, wa-ell you
know-oh oh, we all
wanna change the
world….”
Wait a minute! I
wrote that song!!!
Henry Cavendish
In 1766, Henry
Cavendish mixed a
metal with acid
making flammable
gas which was
lighter than air. We
now know the gas
hydrogen
was _________________
(another element is discovered)
Joseph Priestley
(1733 – 1804)
In 1774, Joseph
Priestley
decomposed
mercuric oxide into
liquid mercury and
a gas. He called the
gas “lively air”
because it made
mice move around
faster!
Antoine Lavoisier
(1743 – 1794)
Antoine Lavoisier
experimented with
Priestley’s gas. He
concluded that air
must be a mixture
of at least 2 gases,
one that supports
burning and one
that does not.
Yeah,
sounds
cool!
Hey! Have you heard
about Priestley’s new
gas?
Cavendish took
some of his “own”
gas (hydrogen) and
using Priestley’s
method produced
some oxygen. He
then burned the
hydrogen in oxygen
and got none other
than water! Of
course, he wrote a
report on this!
I’ve read
Cavendish’s report
and I think I’ve got
it!
When matter is
broken down, the
final form is an
element. You can’t
break it down any
more!
Antoine Lavoisier
Lavoisier’s wife, Marie also
helped in his research but her
contribution is seldom mentioned!
I’m going to
publish all this
stuff, but I don’t
think I’ll mention
Priestley or
Cavendish, or
even Marie, for
that matter. I’ll
also take credit for
naming the two
gases, hydrogen
and oxygen!
Can someone help me?
During the
French
Revolution,
Lavoisier was
unfortunately
executed by the
guillotine!
That was too bad.
He contributed a lot
to our knowledge of
science and
chemistry!
In the early 1800’s,
John Dalton came
up with the ATOMIC
THEORY.
His main points were:
Dalton’s Atomic Theory
1) All matter is made of atoms. Atoms
are indivisible and indestructible.
2) All atoms of a given element are
identical in mass and properties
3) Compounds are formed by a
combination of two or more different
kinds of atoms.
4) A chemical
reaction is a
rearrangement of atoms.
Compounds are composed
of little “balls” called
atoms, joined
together by “bonds”
to form molecules.
crookes tube
J.J. Thomson's Experiments
Using Crooke’s tubes and other
equipment, J.J. Thomson discovered
the electron and measured its e/m
(charge to mass) ratio.
Later, “e” was found and the mass of an
electron was found to be 9.10938188 ×
10-28 grams (much lighter than H)
Thomson’s Plum
Pudding Model
Ernest Rutherford
Rutherford’s Scattering Experiment
Applet on Rutherford's Experiment
Rutherford could not explain why the
electron didn’t fall into the
nucleus and
destroy the atom.
?
I think I
can help!
Neils Bohr
spectra and bohr
Bohr pictured the hydrogen
atom as
having discrete energy “levels”
which the electron could “inhabit”. In it’s
ground state, the electron would be in
the lowest level (n=1)
When the atom was “excited” the
electron could “jump” to a higher
level.
When the electron came back down, it
released energy in the form of light.
Each “jump” would give off light of a
particular wavelength or colour. This
gave rise to hydrogen’s spectrum.
According to Bohr, each energy “level”
corresponded to a different “orbit” of an
electron around the atom. (Like planets
around the sun.)
This model
is really
cool !!
Bohr even calculated what the radii of
these orbits would be.
Element 107 on the
Periodic Table is
called Bohrium (Bh)
In the 1920’s things changed!
Although Bohr’s idea of energy levels
was still accepted, his idea of planetary
orbits for electrons was rejected!
REJECT ! !
So……
What’s Next???
????????????