Transcript Unit 4: History of the Atom
UNIT 4: HISTORY OF THE ATOM
HISTORY OF THE ATOM MODELS OF THE ATOM DALTON’S ATOMIC THEORY MODERN ATOMIC THEORY
LEARNING TARGETS FOR TODAY: • • • • I can state which scientist discovered each particle and cite evidence for how each particle was discovered (DOK 1 and DOK 3). I can explain the historical models of the atom (DOK 2) I can state the charge of each atomic particle (DOK 1) I can locate each atomic particle in the atom (DOK 1)
ANCIENT GREEKS
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There was no science
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No controlled experiments
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Little Technology
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Ideas came from life experiences
DEMOCRITUS (460-370 B.C.)
• • • First to suggest that matter was NOT indefinitely divisible.
Matter was made up of atomos – that which cannot be split Atomos moved through empty space • Atomos could not be created nor destroyed, or divided.
ARISTOTLE (384-322 B.C.)
• • • • • Did not believe in Democritus’s atoms Did not believe in empty space Matter was indefinitely divisible Believed all matter was: Earth, Fire, Water and Air Since he was the leading mind, at the time, no one challenged his ideas of 2000 years.
THE ALCHEMIST: 400-1400 AD
• • • • • First to do “science” First to use experimentation to prove ideas First to use symbols to identify elements Attempted to turn lead into gold Many of their discoveries lead to the modern science of Chemistry
JOHN DALTON 1766 – 1844 AD
• English chemist and meterologist • Revived and revised Democritus’s ideas using scientific research • Matter is made up of atoms • Matter is indivisible and indestructible • Developed the first atomic theory
DALTON’S ATOMIC THEORY (1808)
• • • Atoms of given elements (the same element) are identical in size, mass, and chemical properties.
• Atoms of one element differ from those another element.
Atoms combine in simple whole number ratios to form compounds In reactions, atoms are separated, combined, or rearranged. *Had to be revised as new data was collected.
MODERN ATOMIC THEORY
*Started with Dalton’s Atomic Theory, and was only changed slightly, through new discoveries. • • • • • • Matter is indestructible and made up of atoms Atoms are the smallest particle of an element that retains the properties of a specific element
Atoms of the same element can vary in mass Atoms are divisible, into smaller subatomic particles – protons, neutrons, electrons
Atoms combine in simple whole number ratios to form compounds In reactions, atoms are separated, combined, or rearranged. (Law of Conservation of Matter)
DALTON’S ATOMIC THEORY VS. MODERN ATOMIC THEORY Dalton’s Atomic Theory • • • • • • Matter is indivisible and indestructible Matter is made up of atoms Atoms of given elements (the same element) are identical in size, mass, and chemical properties.
Atoms of one element differ from those another element.
Atoms combine in simple whole number ratios to form compounds In reactions, atoms are separated, combined, or rearranged. • • • • • • Modern Atomic Theory Matter is indestructible and made up of atoms Atoms are the smallest particle of an element that retains the properties of a specific element
Atoms of the same element can vary in mass Atoms are divisible, into smaller subatomic particles – protons, neutrons, electrons
Atoms combine in simple whole number ratios to form compounds In reactions, atoms are separated, combined, or rearranged. (Law of Conservation of Matter)
HOW DOES THE ATOM LOOK?
• • Scientist wanted to know what the atom looked like.
Scientist knew a couple things, and those became the basis for their models: • • Matter was neutral Matter has mass Atoms
J.J. THOMSON (1897) • • • Plum Pudding Model: • Believed the atom was like plum pudding (said the pudding was the positive matter and the plums were negative particles) • The atom was mostly positively charged, but had negatively charged particles embedded in it. (Like chocolate chips in a chocolate chip cookie) • Believed it was spherical shaped Cathode Ray Experiment Discovered the Electron J.J. Thomson
ERNEST RUTHERFORD (1911)
• • • • • • • Gold Foil Experiment Disproved his professor/teacher J.J. Thomson Suggested that atoms have a nucleus Suggested another subatomic particle Hinted to a 3 rd subatomic particle Suggested electrons were “orbiting” the nucleus Proton – Electron Attraction
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GOLD FOIL EXPERIMENT
Shot a beam of radiation at a thin sheet of gold Hypothesis was based on the Plum Pudding Model Expected particles to go straight through the piece of gold foil, unless they hit an electron • Some particles were reflected back to the firing machine, and then deflected in different directions.
• He expected that some would be deflected as they hit an electron here and there, but he did not expect ANY to be reflected.
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GOLD FOIL EXPERIMENT
Shot a beam of radiation at a thin sheet of gold Hypothesis was based on the Plum Pudding Model Expected particles to go straight through the piece of gold foil, unless they hit an electron • Some particles were reflected back to the firing machine, and then deflected in different directions.
• He expected that some would be deflected as they hit an electron here and there, but he did not expect ANY to be reflected. *Lead to Rutherford’s model and idea about the Atom – giving shape to the Modern Atomic Theory.
ERNEST RUTHERFORD (1911) • • • • Atom is made up of mostly empty space • Electrons moved around in the empty space Positive part of the atom was at it’s center • Nucleus – a small dense positively charged space at the center of an atom Electrons were held within the atom due to their attraction to the nucleus • Electrons are attracted to the positive charge of the nucleus, keeping them attached to that atom, and not drifting in space.
The diameter of the atom was calculated to be 10,000 times the diameter of the nucleus • If an atom were 2 football fields, the nucleus would be a nickel
ERNEST RUTHERFORD (1920) • • • • The Nucleus • Made up of protons and another subatomic particle • • Makes up 99.97% of the atom’s mass Protons are a positively charged subatomic particle • Another subatomic particle with a neutral charge Electrons • Negatively charged • • Surround the nucleus, not in the nucleus Found on the electron cloud • • Negligible to the mass of an atom Attracted to the positive charge of the protons in the nucleus Protons and electrons are attracted to each other Atoms are mostly empty space Rutherford
JAMES CHADWICK (1932) • • • • English Physicist Won the Nobel Prize in Physics in 1932 • For his discovery of the neutron Student of Rutherford • • Cofound the neutron Proved the existence of the 3 rd subatomic particle – Rutherford’s idea The Neutron • • Contributes, almost equally as the proton does, to the atom’s mass Electrically neutral – how it got it’s name
GELL-MANN AND ZWEIG (1964) • • • Proposed that protons and neutrons were made up of smaller particles Little is known about these particles They are called “quarks” – overall term Quarks Quarks 2
MODERN ATOMIC THEORY • Follows Rutherford’s ideas and model of the atom from 1920 • Protons and Neutrons are divisible into smaller particles called quarks • Quarks are still in their infancy in the world of science • they are still a new discovery and still being figured out
HOMEWORK
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Complete page 1 front and back: What is Matter
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