Thursday, Oct 26 Friday, Oct 27

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Thursday, Oct 26Friday, Oct 27

• Atomic theory Continued
• Hmwk
• Read Chapter 4, Sect. 2 Ques 1-2, 4-6

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Agenda

• Warm-Up Paper Division Discussion
• Notes Atomic Theory and Atomic Structure
• Activity Atoms in a Bag
• Video The Atomic Theory

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How many times did you cut the paper strip in
half last class?
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Review What is an atom?

• Atom Smallest particle that retains properties
  of element.

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What particles make up an atom?

• Particle Charge Mass
• Electron -1 0
  amu
• Proton 1 1 amu
• Neutron 0 1 amu

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Review Atomic Theory

• Democritus Greek the universe is made up of
  invisible particles called atoms.
• Atom unable to be divided
• Greeks 4 elements earth, water, air, fire

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Daltons Atomic Theory (1808)

• 1) All matter is made of atoms. Atoms are
  indivisible.
• 2) All atoms of a given element are identical.
• 3) Compounds are formed by a combination of two
  or more different kinds of atoms.
• 4) A chemical reaction is a rearrangement of
  atoms.
• Not true

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Notes How were atoms discovered? Electrons

• English physicist J.J. Thomsen
• Discovered the negatively charged electron while
  working with electricity and cathode ray tubes.
  

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Nucleus/protons

• Ernest Rutherford
• gold foil experiment ---- hypothesized a dense,
  positively charged core (nucleus)
• positive charges were protons

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Rutherford

• Electrons Surround a dense nucleus (positive).
  Space around nucleus empty.
• So why dont electrons fall into nucleus?

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Neutrons

• James Chadwick (co-worker of Rutherford)
  bombarded beryllium foil with alpha particles and
  noticed a neutral radiation coming out.
• neutron no electrical charge

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Bohr model

• Electrons in orbits around positive nucleus.
• Energy levels Areas where electrons are likely
  to be found.
• More energy is required to boost an electron to a
  higher energy level.

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Quantum Mechanical Model

• ?Similar to Bohr, except it does not define the
  exact path, but the probability of where an
  electron is.
• Quantum amount of energy to change levels.

90 Chance of finding an electron inside this
line
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Information on Periodic Table

• Atomic Number Number of protons in atom
• Symbol of element
• Name of element
• Atomic mass Average mass of the all the isotopes
  for the element
• (neutronsprotons)

6 C Carbon 12.011
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What is an Isotope?

• Average of all the masses of the atom, including
  the atoms isotopes.
• Isotope has the same number of protons, but has a
  different number of neutrons.

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How will we know if something is an isotope?

• Usually symbol will indicate if its an isotope.
• Carbon-14
• Lithium - 8
• If it doesnt match the listing on the periodic
  table

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Atom in a bag activity

• Complete at least 15 of the bags.
• DO NOT open the bags!
• Calculate protons, electrons, neutrons
• Symbol of element ( protons atomic number)
• Check if its an isotope ( does it match the
  listing on the periodic table---- check number of
  neutrons)

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Atoms in a Bag Create a Data Table
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Atom in a bag Conclusion Questions

• Why are these atoms in a bag not a true
  representation of an atom? (give 2 reasons)
• How are isotopes different than the atoms
  displayed in the periodic table?
• What particle determines the identity of the
  atom? ( protons, electrons or neutrons)

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The Atomic Theory

• Great Discoveries in Chemistry - Video

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Quiz

• How many protons are in Nitrogen?
• How many electrons are in Nitrogen?
• What is the mass number of Nitrogen?
• How many neutrons are in Nitrogen?
• What element has 20 protons, 20 electrons and 20
  neutrons?