8th Grade Physical Science

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8th Grade Physical Science

• Notes Chapter 4 Section 1
• Introduction to Atoms

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John Dalton What did he do?
Daltons Big Ideas

• Elements are composed of indivisible atoms.
• Atoms of the same element are exactly alike and
  have the same mass.
• Atoms of one element cannot be changed to
  another. Atoms cannot be created or destroyed by
  chemical change, only rearranged.
• All compounds are composed of atoms of different
  elements.

John Dalton (1766 1844) was an English
scientist who was interested in physics,
chemistry, and meteorology.
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J. J. Thompson What did he do?
The Plum or Figgy Pudding model of the atom.
Notice the evenly distributed negatively charged
particles in the positive particle

• By experiment found that atoms have negatively
  charged particles (electrons).
• Proposed that atoms must also contain a positive
  charge to remain neutral.
• Described the figgy pudding model where
  electrons are evenly distributed throughout a
  ball of positive charge.

J. J. Thompson (1856 1940) was another English
scientist who won the Nobel Peace Prize in
physics for the discovery of the electron,
isotopes, and the invention of the mass
spectrometer.
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Ernest Rutherford What did he do?
Rutherfords Model of the atom.

• Conducted an experiment that showed an atoms
  nucleus had to have positively charged particles
  (protons).
• He showed that an atom is mostly empty space with
  electrons moving around the nucleus.

Ernest Rutherford (1871 1937) yet another
English scientist and a student of J. J.
Thompsons . He also won a Nobel Prize.
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Niels Bohr What did he do?
Bohrs model of the atom, which can be thought of
as having layers. Just like an onion.

• Changed the atomic model by showing that
  electrons have specific amounts of energy and
  move in orbits.
• These electron orbits resemble planets orbiting
  the sun.

Niels Bohr (1885 1962) was a Danish scientist
who worked on the Manhattan Project, won a Nobel
Peace Prize, and was a buddy of Albert Einsteins.
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What is the Cloud Model?

• Electrons have different amounts of energy that
  determine how and where it moves in an atom.
• This is known as the energy level.
• Electrons appear to be able to move anywhere in
  the energy level and do not orbit like planets.

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James Chadwick What did he do?

• Discovered another particle in the nucleus of the
  atom.
• This particle has no charge and was named the
  neutron.
• Neutrons have a mass that is about equal to the
  mass of a proton.

James Chadwick (1891 1974) an English physicist
and Nobel Laureate.
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What does the modern atomic model look like?

• The center of the atom is the tiny nucleus, which
  contains most of the mass of the atom.
• The nucleus contains the protons and neutrons

• Surrounding the nucleus is the cloudlike region
  of swiftly moving electrons.
• The atom is composed of mostly empty space.

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What does the modern atomic model look like?
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What does the modern atomic model look like?

• Atoms are small. Only recently have we been able
  to glimpse atoms using very specialized, very
  powerful electron microscopes.
• Every atom of an element has the same number of
  protons. The number of protons is the atomic
  number.

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What does the modern atomic model look like?

• The number of neutrons is not a fixed number for
  an element. Atoms of elements that have different
  numbers of neutrons from each other are isotopes.
• Ex. Carbon atoms have 6 protons and 6 electrons,
  but the neutrons can be 6,7, or 8.

• Isotopes have a mass number and it is part of the
  name for the atom. The mass number is the protons
  plus the neutrons.
• Ex. Carbon 12, Carbon 13, and Carbon 14.