The History of the Atom From Democritus to Today’s Modern Theory.
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The History of the Atom From Democritus to Today’s Modern Theory
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Transcript of The History of the Atom From Democritus to Today’s Modern Theory.
The History of the AtomFrom Democritus to Today’s Modern Theory
Democritus• 400 BC• Proposed that all matter is made up of
atoms.• Thought atoms were small, hard particles
of different shapes and sizes.• Coined the term ‘Atom’
– From the Greek word meaning ‘Can not be divided.’
Alchemists
• First ‘Chemists’ around 900 AD• First to include observation and
experimentation with pure thought methods of science.
Lavoisier
• 1785• Authored the Law of Conservation of
Mass• Did experiments to prove that matter
does not disappear during a chemical reaction.
• ‘Matter can not be created or destroyed, it can only be rearranged.’
Dalton• Father of Modern Atomic Theory • 1800’s• All matter consists of atoms with space in
between.• Atoms of the same kind of element are
identical to each other.• There are as many different kinds of
atoms as there are different elements.• Atoms are solid spheres.• ‘Billiard Ball Model’
Thomson
• 1904• Inferred that atoms contain small
negatively charged particles.• He called them ‘electrons.’• He thought the electrons were dispersed
throughout a positively charged sphere.• ‘Chocolate Chip Cookie Dough Model’
Rutherford
• 1911• Famous Gold Foil Experiment• Discovered and named the ‘nucleus’ of
the atom.• Proposed that most of the mass and all of
the positive charges of an atom are in its nucleus.
• ‘Peach Pit Model’
Rutherford’s Gold Foil Experiment
Peach Pit Model
Bohr
• 1913• Concluded that electrons travel in fixed
orbits around the nucleus based on the amount of energy they contain.
• He called the ‘orbits’ Energy Levels.• ‘Solar System Model’
Erwin Schrodinger and Werner Heisenberg
Schrodinger and Heisenburg
• 1926• Scientists described the electron region of
the atom as a cloud around the nucleus.• This cloud area shows that electrons do
not orbit the nucleus in definite paths, but are likely to be in a given region at any particular time.
• ‘Modern Electron Cloud Model’
Chadwick
• 1932• Worked with E. Rutherford in the
discovery of a third sub-atomic particle.• He concluded this particle to be free of
electrical charge and he called it the ‘neutron.’
• Concluded it was located in the nucleus along with the protons.
Chadwick’s Discovery of the Neutron
Today’s Newest Members:
Quarks and Leptons• Particles within particles.• Protons and Neutrons are made of
Quarks:Up DownStrange TopCharm Bottom
• Electrons are a small thin type of Lepton.
And now you know the rest of the story!!The End.
