Evolution of Atomic Theory Through the Ages

 
DO NOW
 
Pick up notes handout
Turn in Cha-Cha-Cha-Changes lab.  Is
your partner’s name on it????
 
The Development of the
The Development of the
Atomic Theory
Atomic Theory
 
Democritus to Rutherford
 
What do you know about
What do you know about
the atom?
the atom?
450 BC
450 BC
 
Greek - Democritus
Atom was
indivisible.
Theorized the
existence of the
atom.
Also, theorized that
there were just four
'elements' -  fire, water,
air, earth.
 
1760
1760
 
Benjamin Franklin
discovers that an
object can have an
electrical charge
.
Charge can be
positive or negative.
1803
1803
 
John Dalton
1.  Atom was 
indivisible
.
2.  All 
elements
 are composed of atoms.
3.  The same atoms for one element are 
exactly
alike.
4.  Atoms are neither created or destroyed in a
chemical reaction.
5.  In a chemical reaction, atoms are 
separated
,
combined
, or 
rearranged
.
6.  Different atoms combine in 
simple
 
whole
number ratios to form compounds.
1880
1880
 
Sir William Crookes
determined that rays were traveling from
one end to another in the cathode ray
tube
CATHODE RAY TUBE
CATHODE RAY TUBE
 
Others experimented with the cathode ray tube
and discovered that the type of gas had no effect
so the ray must be a part of all matter.
A magnet deflected the ray, so it must be
composed of charged particles, and it deflected
toward the positive, so the charged particles must
be negative.
Late 1890s
Late 1890s
 
J. J. Thomson
discovered the 
electron
 using the
cathode ray tube .
determined that the electron was smaller
than a 
hydrogen
 atom.
Knew the atom was neutral and the
electron was negative, so there must be
positive material with a lot more mass.
J. J. THOMSON
J. J. THOMSON
 
Said the atom was a 
positive
 pudding-like
material throughout which 
negatively
charged electrons were scattered  -  Plum
Pudding or Chocolate Chip Cookie
Model
1909
1909
 
Robert Millikan
Measured the mass of an 
electron
.
Knew the electron was negative, but
determined the charge (as a
measurement).
Was able to use this measurement to
determine the mass of an electron.  It
was 
1/1840
 of a hydrogen atom.
 
VIDEO
VIDEO
1909
1909
 
Ernest Rutherford
Did famous 
gold foil 
experiment (the
alpha scattering experiment).
Calculated that the atom was 
mostly
empty
 space through which electrons
move.
Concluded that the atom has 
a small,
dense, positively charged, centrally-
located nucleus surrounded by
negatively charged electrons.
1919
1919
 
Ernest Rutherford
He had refined the concept of the
nucleus.  Called the positive particles
protons
.
1932
1932
 
Ernest Rutherford and
James Chadwick
showed the nucleus also
had 
neutrons
.
The neutron was
basically equal in mass to
the proton but had 
no
electrical
 charge –
considered 
neutral
.
 
 
1914
 
Neils Bohr
Concluded that
the 
electrons
moved around the
nucleus in definite
orbits or 
energy
levels.
QUANTUMMECHANICAL
MODEL - CURRENT
 
Electrons
 do not move in
definite orbits.
The 
exact
 location of an
electron in an atom is
impossible
 to determine.
The electron location can
only be spoken of in terms of
a probability of being in a
particular location.
THE DIVISIBLE ATOM
THE DIVISIBLE ATOM
Is 
indivisible
 .
Composes 
all
 elements.
The same atoms for one element are
exactly alike.
Atoms are neither 
created or destroyed
in a chemical reaction.
Atoms are 
separated
, 
combined
, or
rearranged
 in a chemical reaction in
simple whole number ratios.
 
FALSE - divisible
 
FALSE – not alike
 
TRUE
 
TRUE
 
TRUE
ATOMIC THEORY to this
ATOMIC THEORY to this
point
point
 
is spherically shaped with a dense, centrally
located, positive nucleus surrounded by one or
more negatively charged electrons in an electron
cloud.
Most of the atom consists of fast moving
electrons traveling through empty space
surrounding the nucleus.
Electrons are held within the atom by an
attraction to the positive nucleus.
The nucleus has neutral neutrons and positive
protons and 99.9% of the mass.
Since atoms are electrically neutral, the number
of protons must equal the number of electrons.
THE ATOMIC THEORIES
THROUGH TIME
 
TO DO
 
Handout due Wednesday.
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Explore the fascinating journey of the atomic theory from the ancient ideas of Democritus in 450 BC to the groundbreaking discoveries by scientists like Benjamin Franklin, John Dalton, Sir William Crookes, J.J. Thomson, and more. Witness the evolution of our understanding of atoms and their structure, from the indivisible concept of Democritus to Thomson's Plum Pudding Model.

  • Atomic theory
  • Democritus
  • John Dalton
  • J.J. Thomson
  • Evolution

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  1. DO NOW Pick up notes handout Turn in Cha-Cha-Cha-Changes lab. Is your partner s name on it????

  2. The Development of the Atomic Theory Democritus to Rutherford

  3. What do you know about the atom?

  4. 450 BC Greek - Democritus Atom was indivisible. Theorized the existence of the atom. Also, theorized that there were just four 'elements' - fire, water, air, earth.

  5. 1760 Benjamin Franklin discovers that an object can have an electrical charge. Charge can be positive or negative.

  6. 1803 John Dalton 1. Atom was indivisible. 2. All elements are composed of atoms. 3. The same atoms for one element are exactly alike. 4. Atoms are neither created or destroyed in a chemical reaction. 5. In a chemical reaction, atoms are separated, combined, or rearranged. 6. Different atoms combine in simple whole number ratios to form compounds.

  7. 1880 Sir William Crookes determined that rays were traveling from one end to another in the cathode ray tube

  8. CATHODE RAY TUBE Others experimented with the cathode ray tube and discovered that the type of gas had no effect so the ray must be a part of all matter. A magnet deflected the ray, so it must be composed of charged particles, and it deflected toward the positive, so the charged particles must be negative.

  9. Late 1890s J. J. Thomson discovered the electron using the cathode ray tube . determined that the electron was smaller than a hydrogen atom. Knew the atom was neutral and the electron was negative, so there must be positive material with a lot more mass.

  10. J. J. THOMSON Said the atom was a positive pudding-like material throughout which negatively charged electrons were scattered - Plum Pudding or Chocolate Chip Cookie Model

  11. 1909 Robert Millikan Measured the mass of an electron. Knew the electron was negative, but determined the charge (as a measurement). Was able to use this measurement to determine the mass of an electron. It was 1/1840 of a hydrogen atom.

  12. VIDEO

  13. 1909 Ernest Rutherford Did famous gold foil experiment (the alpha scattering experiment). Calculated that the atom was mostly empty space through which electrons move. Concluded that the atom has a small, dense, positively charged, centrally- located nucleus surrounded by negatively charged electrons.

  14. 1919 Ernest Rutherford He had refined the concept of the nucleus. Called the positive particles protons.

  15. 1932 Ernest Rutherford and James Chadwick showed the nucleus also had neutrons. The neutron was basically equal in mass to the proton but had no electrical charge considered neutral.

  16. 1914 Neils Bohr Concluded that the electrons moved around the nucleus in definite orbits or energy levels.

  17. QUANTUMMECHANICAL MODEL - CURRENT Electrons do not move in definite orbits. The exact location of an electron in an atom is impossible to determine. The electron location can only be spoken of in terms of a probability of being in a particular location.

  18. THE DIVISIBLE ATOM Is indivisible . Composes all elements. The same atoms for one element are exactly alike. Atoms are neither created or destroyed in a chemical reaction. Atoms are separated, combined, or rearranged in a chemical reaction in simple whole number ratios. FALSE - divisible TRUE FALSE not alike TRUE TRUE

  19. ATOMIC THEORY to this point is spherically shaped with a dense, centrally located, positive nucleus surrounded by one or more negatively charged electrons in an electron cloud. Most of the atom consists of fast moving electrons traveling through empty space surrounding the nucleus. Electrons are held within the atom by an attraction to the positive nucleus. The nucleus has neutral neutrons and positive protons and 99.9% of the mass. Since atoms are electrically neutral, the number of protons must equal the number of electrons.

  20. THE ATOMIC THEORIES THROUGH TIME

  21. TO DO Handout due Wednesday.

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