ATOMS: The Building Blocks of Matter

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ATOMS The Building Blocks of Matter

• Objectives
• Law of conservation of mass
• Law of definite proportions
• Law of multiple proportions
• Daltons Atomic Theory
• How Daltons Atomic Theory relates to 1, 2, 3

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Atomic Theory Foundations

• Law of Conservation of Mass mass is neither
  created or destroyed during a chemical or
  physical change
• Law of Definite Proportions a compound contains
  the same proportions by mass regardless of the
  size of the sample
• Example
• NaCl always 39.34 Na 60.66 Cl

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Atomic Theory Foundations

• 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
• Example
• CO2 and CO ratio of oxygen is always 21

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Daltons Atomic theory

1. All matter is composed of atoms
2. Atoms of an element have the same size, mass and
   properties atoms of a different element have
   different sizes, masses and properties
3. Atoms cannot be divided, created or destroyed
4. Atoms of different elements combine in simple
   whole number ratios
5. Chemical reactions combine, separate, or
   rearrange atoms

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Modern Atomic Theory

• Atoms can be divided
• Atoms of the same element can have different
  masses
• All else remains the same

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Structure of the Atom

• Objectives
• Discovery of the Electron
• Rutherfords Experiments
• Protons, Neutrons, Electrons

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Atomic Structure

• Electron no mass negative charge
• Proton mass hydrogen atom positive
• Neutron mass hydrogen atom no charge
• Daltons Model
• JJ Thompsons Plum Pudding Model

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Rutherford

• Shoots alpha particles (Helium atoms) at gold
  foil
• Expected to pass right through
• Particles are deflected
• Leads to idea of a dense positively charged
  center with e- orbiting around it

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The electron

• Mass of 9.109 x 10-31 kg
• Negative charge

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The Proton

• Mass 1.673 x 10-27 kg
• Positive charge

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The neutron

• Mass 1.675 x 10-27 kg
• No charge

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Comparing Theories
Dalton See notes Solid sphere Thompson Plum pudding model Electrons scattered thru positively charged cloud Rutherford Concept of the nucleus Positively charged
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Counting Atoms

• Objectives
• Explain isotopes
• Define atomic number, atomic mass
• Determine number of protons, neutrons electrons
• Define mole and molar mass
• Convert between grams, moles, and atoms

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Atomic Number

• Atomic Number
• of protons in nucleus
• Element Symbol
• Element Name
• Atomic Weight
• Electron Configuration

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Li
Lithium 6.914 He2s1
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Isotopes

• Def atoms of the same element that have
  different masses
• Example hydrogen
• protium 1 proton in nucleus
• deuterium 1 proton 1 neutron
• tritium 1 proton 2 neutrons
• Nuclide general term for any isotope

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Mass Number

• Def the number of protons and neutrons in the
  nucleus of an isotope
• mass - atomic of neutrons
• Example oxygen
• Mass (16) atomic (8) of neutrons (8)

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Writing Isotopes
Example Uranium 235
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