Summarize the five essential points of Dalton

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Chapter 3-1 The Atom

• Summarize the five essential points of Daltons
  atomic theory
• Explain the relationship between Daltons Atomic
  Theory and the laws of conservation of mass and
  definite composition
• Explain the law of multiple proportions.

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Early Ideas of the Atom

• Democritus
• Greek Philosopher
• 460-370 B.C.
• Stated Matter could be divided into smaller
  smaller particles until it could no longer be
  divided.
• Called these Particles Atomos (indivisible)
• Not based on any physical evidence, only thought

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Daltons Atomic Theory

• Late 1700s John Dalton School
  Teacher(england)
• Daltons Atomic Theory Summarized

1. All matter is composed of extremely small
   particles called atoms.
2. Atoms of a given element are identical in size,
   mass, and other properties. (Isotopes - atoms
   same element with different mass.)
3. Atoms cannot be subdivide, created, or destroyed.
4. Atoms of different elements can combine in
   simple, whole-number ratios to form chemical
   compounds.
5. In chemical reactions, atoms are combined,
   separated, or rearranged.

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Law of Conservation
Law of Definite Composition

• Atoms and the conservation of mass
• If atoms are indivisible
• mass must be conserved
• A B ? AB

Law of Constant Composition A compound always
contains the same elements in the same
proportions by mass. The mass ratio of A to B
will always be the same. In this case 13 or 25
to 75
1 a.u. 3 a.u. ? 4 a.u.
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Law of Multiple Proportions

• If two or more different compounds are composed
  of the same two elements, then the ratio of the
  masses of the second element combined with a
  certain mass of the first element is always a
  ratio of small whole numbers.
• CO2 1g to 2.66g CO 1g to 1.33g
• Ratio of oxygen would 21.

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Law of Definite ProportionsCalculations

• Hydrogen and Oxygen have a mass ratio of 116.
  What is the mass of oxygen needed to form with
  14g of Hydrogen? What is the total mass of this
  compound?

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Law of Definite ProportionsCalculations

• Magnesium and Oxygen have a mass ratio of 32.
  What is the mass of oxygen needed to form with
  20g of Magnesium? What is the total mass of this
  compound?

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3.2 Discovering Atomic Structure

• Particle arrangement of the atom.
• Protons ()
• Electrons (-)
• Neutrons (0)
• Michael Faraday
• Made the connection between the atom and
  electricity.

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J.J Thomson

• Used a Cathode Ray Tube (CRT)
• Discovered electrons
• Charge and mass
• Electric current passed through low pressure gas
  in a glass tube.

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Robert Millikan

• Millikans Oil-Drop Experiment
• Proved the mass and charge of all electrons are
  identical.
• Used an electric plate created a resistant force
  acting on falling particles
• Voltage Controlled
• By varying the charge on
• different drops, he noticed
• that the charge was always a
• multiple of -1.6 x 10 -19 C.

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Ernest Rutherford

• Used the Gold Foil Experiment
• Marsden and Gieger proved the existence of the
  nucleus
• Bombarded thin sheets of metal with () charged
  particles.
• Results of the Particle deflections
• Most traveled through
• Some Deflected in Both Directions
• Very Few Deflected Back

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Rutherford vs. Thomson
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Rutherford results

• Atom
• Nucleus
• Central part of the atom.
• Very small and very massive Very dense.
• All the mass of an atom.
• Positively charged, location of protons.
• Electrons
• Surround the nucleus, gives size to the atom.
• Negatively charged, atom itself is electrically
  neutral.

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E. Goldstein

• Used canal rays in a cathode ray tube to prove
  the existence of protons.
• Positively charged particles that had significant
  mass moved towards the cathode.

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Sir James Chadwick

• Using kinematics, Chadwick was able to determine
  the velocity of the protons. Then through
  conservation of momentum techniques, he was able
  to determine that the mass of the neutral
  radiation was almost exactly the same as that of
  a proton. .
• Neutrons, were neutrally charged particles found
  in the nucleus to add mass to the atom and to act
  as nuclear glue.

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Summary of the Atom

• Nucleus - very dense, ()charged, center of an
  atom.
• Protons
• Positively charged particle found in the nucleus
• Gives mass to the atom.
• Neutrons
• Neutrally charged particle found in the nucleus.
• Gives mass to the atom and acts as nuclear glue
• Electrons
• Negatively charged particles that give the atom
  its size.

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3.3 Modern Atomic Theory
Properties of Subatomic Particles
Particle Symbols Relative Charge Mass Number Relative Mass Actual Mass
Electron e- -1 0 0.00055 u 9.11 x 10-28g
Proton p 1 1 1.00728 u 1.67 x 10-24g
Neutron n0 0 1 1.00866 u 1.68 x 10-24g
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Atomic Mass Units (amu)

• the equivalent mass of an atom.
• Protons 1amu
• Neutrons 1amu
• Electrons 0 amu

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Subatomic calculations

• Atomic Number (Z) the number of protons within
  an atom. (Atomic p)
• Every element has its own unique atomic number.
• p e- , in an atom
• Mass p n0

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Isotope Abbreviations

• Atomic Symbol Notation
• X atomic symbol

• Mass Number form
• name of element mass

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Isotope Form Practice

• Write the element uranium with a mass of 235 in
  atomic and mass form
• Mass
• Atomic form

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Subatomic Particle Practice

• How many protons, neutrons and electrons do the
  following contain?
• Carbon 13

• Carbon
• p
• e-
• no

Gold p e- n0
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e-
n0
p
Mass
Atomic
Mass Form
Symbolic Form
30
33
30
63
30
Zinc-63
76
115
76
191
76
Osmium-191
74
106
74
180
74
Tungstun-180
56
83
56
139
56
Barium-139
25
28
25
53
25
Manganese-53
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Isotopes

• Atoms of the same element with different mass,
  due to the number of neutrons.
• The number of protons determines the identity of
  an atom !!!!!!!
• The number of neutrons can be different for the
  same type of element.
• Hydrogen

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Hydrogen Isotope Names

• 3 isotopes of hydrogen
• Protium, Hydrogen 1
• Deuterium, Hydrogen 2
• Tritium, Hydrogen 3

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Relative Atomic Masses

• Although we know actual masses of atoms it is
  more practical to use their relative masses
• The arbitrary point Carbon-12
• 1 atomic unit (a.u.) Exactly 1/12 of C-12
• All other atoms, weighed based upon Carbon-12

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Atomic Mass

• Average mass of all naturally occurring isotopes
  of an element.
• Calculation
• Atomic mass (mass of each isotope)(
  abundance)/100
• Add the answers to each of the isotopes to get
  the average mass.

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Modern Atomic Theory

• Determine the atomic mass of Oxygen.

Isotope Mass (amu) abundance
Oxygen 16 15.994915 99.762
Oxygen 17 16.999131 .038
Oxygen 18 17.999160 .200
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Modern Atomic Theory
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Modern Atomic Theory

• Determine the atomic mass of Uranium.

Isotope Mass (amu) abundance
Uranium-235 235.043924 .720
Uranium - 238 238.050784 99.280
Uranium
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Relating Mass to Particles

• The Mole
• The number of atoms of an element equal to the
  number of atoms in exactly 12.0 g of carbon-12.
• Referred as a counting number.
• 1 mole of any element 6.02 x 10 23 atoms
• Avogadros number, there are exactly 6.02 x 1023
  atoms of any element in 1 mole of that element.
• 1mol C
• 1mol H
• 1mol S

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Molar Mass

• Mass in grams of 1 mole of any substance.
• Equivalent to the formula mass of a compound and
  to the atomic mass of an element.
• 1 mol of S 32g S
• 1 mol of C 12g C

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Mole Conversions

• 1 mol Formula mass (or Atomic Mass)
• Or the Molar Mass
• 1 mol 6.02 x 10 23 particles
• The mole is the central unit in converting the
  amount of substances in chemistry.

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Mass Mole Conversions

• Use 1 mol Formula Mass conversions.
• Mass to Moles Conversion
• How many moles are in 250.g of Na?

• Moles to Mass Conversion
• How many grams are in .55 moles of C?

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Practice Mass-Mole

• Determine the number of moles in the following
  substances
• 6.60g N
• 100.g Fe

• Determine the mass for the following substances
• 3) 6.25 mol Cu
• 4) .650 mol P

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Mole Particle Conversion

• Use 1 mol 6.02 x 10 23 particles
• Particle to Mole Conversion
• How many moles are equivalent to 550. atoms of S?

• Mole to Particle Conversion
• How many atoms are in .525 moles of Ca?