Matter

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Matter The Atom
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Matter

• The term matter describes all of the
  physical substances around us your table, your
  body and a pencil
• Anything that has mass and takes up space (has
  volume)
• Made up of different kinds of atoms

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Matter is made of atoms
Atoms are the smallest particles of an element,
having all the characteristics of that element.
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Models

• Models are often used for things that are too
  small or too large to be observed or that are too
  difficult to be understood easily

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Models

• In the case of atoms, scientists use large models
  to explain something that is very small
• Models of the atom were used to explain data or
  facts that were gathered experimentally.
• So, these models are also theories

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Early Models of the Atom Democritus

• 440 B.C.
• Universe was made of empty space and tiny bits of
  stuff
• Called these tiny bits of stuff atomos
• Atoms could not be divided
• Single Material
• Form different materials by joining together

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Early Models of the Atom Dalton

• 1803
• All substances are made of atoms small, cant be
  created, divided, or destroyed.
• Atoms of the same element are the same
• Atoms of different elements are different.
• Compounds consisted of atoms of different
  elements combined together in specific
  proportions

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Early Models of the AtomThomson

• 1897
• Plum pudding model
• Looks like chocolate chip ice cream.
• Atom made of a positively charged material with
  the negatively charged electrons scattered
  through it.

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Early Models of the Atom Rutherford

• 1911
• Mostly empty space
• Small, positive nucleus
• Contained protons
• Negative electrons scattered around the outside
• Planets around the sun

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Early Models of the Atom Bohr

• 1913
• Electrons move in definite orbits around the
  nucleus
• Electrons jump from level to level

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Modern Model of the AtomThe electron cloud

• 20th Century
• Sometimes called the wave model
• Spherical cloud of varying density
• The cloud shows where an electron is more or less
  likely to be

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Atomic Model Review

• Section Review Pg 83 and 86
• 1.
• 2.
• 3.
• 1.
• 2.
• 3.

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Atomic Structure

• Nucleus
• Protons
• Neutrons
• Electron Cloud
• Electrons

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Atomic Structure

• Electrons
• Tiny, very light particles (0amu)
• Have a negative electrical charge (-)
• Move around the outside of the nucleus

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Atomic Structure

• Protons
• Much larger and heavier than electrons (1 amu)
• Protons have a positive charge ()
• Located in the nucleus of the atom 

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Atomic Structure

• Neutrons
• Large and heavy like protons (1 amu)
• Neutrons have no electrical charge
• Located in the nucleus of the atom 

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Atomic Structure
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Describing Atoms

• Atomic Number number of protons
• In a neutral atom, the of protons the of
  electrons

6 C Carbon 12.0
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Describing Atoms
6 C Carbon 12.0

• Atomic Mass Number
• equal to the number of protons plus neutrons.

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Describing Atoms

• Atomic Weight
• average mass of the naturally occurring isotopes
  of an element.
• Isotopes
• atoms that have the same number of protons but
  have different numbers of neutrons

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Isotopes

• The number of protons for a given atom never
  changes.
• The number of neutrons can change.
• Two atoms with different numbers of neutrons are
  called isotopes

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Isotopes

• Have the same atomic number (number of protons)
• Have different atomic mass numbers (number of
  protons neutrons)

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Isotopes
Carbon Nucleus- Same number of Protons different
number of Neutrons.
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Ions

• An atom that carries an electrical charge is
  called an ion

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Ions

• If the atom loses electrons, the atom becomes
  positively charged (because the number of
  positively charged protons will be more the
  number of electrons)
• If an atom gains electrons, the atom becomes
  negatively charged (more negative charges than
  positive charges)

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Ions

• The number of protons does not change in an ion
• The number of neutrons does not change in an ions
• So, both the atomic number and the atomic mass
  remain the same.

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Ions
This atom has lost an electron. Now it has one
more proton than electron. One more proton means
one more positive charge. This makes the total
charge of the atom POSITIVE.
This atom has gained an electron. Now it has one
less proton than electron. One less proton means
one less positive charge. This makes the total
charge of the atom NEGATIVE.