Atomic Structure and The Periodic Table

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Atomic Structure and The Periodic Table

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• Mr. Chan
• Northwestern University

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Today (Day 18)

• (0-10) Return/Discuss Tests
• (10-15) Activate Sketch Atom
• (15-20) Mystery Box
• (20-30) Daltons Atomic Theory
• (30-43) Word Splash
• Video WOC The Atom (30 min)
• Conferences

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Mystery Boxes

• Procedure
• Select a Mystery Box. Without opening it, try to
  learn about its contents by using all the tools
  of observation available to you. Outline your
  plan to determine the contents of the box and
  record all observations you make.

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Mystery Boxes

• Questions
• 1. What evidence supports your conclusion about
  the type of item contained in the box?
• 2. What kinds of things can you do to determine
  the contents of your box if you had access to
  other kinds of observational tools?
• 3. Since you cannot see what is inside, how can
  you be 100 sure of its contents?

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What are atoms?

• Smallest particle of element that retains
  properties of the element
• Possible to see individual atoms
• Demo Al Foil Physical Changes Smallest Piece

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History of Atomic Theory

• Original model Democritus
• Atomos smallest unit of matter
• Daltons Theory
• 1) Elements composed of tiny indivisible (not
  invisible) particles called atoms
• 2) Atoms of the same element are identical
• 3) Atoms of different elements can chemically
  combine with one another in simple whole number
  ratios (compounds)
• 4) In chemical reactions, atoms are separated,
  joined, and rearranged. Atoms of one element are
  never changed.

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Today (Day 19)

• (0-5) Discuss HW
• (5-10) Demo
• (10-25) Experiments discovery of Atomic
  Structure
• (25-35) Rutherfords Au Experiment
• (35-43, 0-25) LAB
• (25-43) Numbers associated with At.Structure

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What is the structure of an atom?

• Electrons
• J.J. Thomson, cathode ray tubes Overhead
• Electric current flowing through gases
• Beam cathode ray travels from cathode (-) to
  the anode ()
• Metal plates beam attracted to positive plate
• Electrons negative, 1/2000 mass of hydrogen
  atom
• Millikan oil drop experiments
• determined charge/mass ratio of electron
• Mass of electron 1/1840 mass of hydrogen atom

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Structure cont.

• Protons positively charged particles
• Needed to balance charge of electrons in atom
• Goldstein CRT with loss of electrons canal
  rays from cathode traveling in opposite direction
  as electrons
• Neutrons no charge, mass - proton
• Chadwick knew some mass was unaccounted for

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Summary of Subatomic particles

• Particle, symbol, relative charge, relative mass,
  actual mass

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Rutherfords Gold Foil Experiment
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Rutherfords Gold Foil Experiment

• Led to discovery that most of the atom is empty
  space
• All of the positive charge and most of the atoms
  mass found in a small region
• Nucleus of the atom
• Core that contains protons and neutrons

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Models of Atoms
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Numbers Associated with Atomic Structure

• Atomic Number
• Number of protons in nucleus of atom of element
• Also equals number of electrons if electrically
  neutral
• Determines which element you have
• Practice How many protons and electrons, what
  the symbol, element name is
• Mass number
• Total number of protons and neutrons
• Not given on the periodic table

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Calculating Number of Protons, Neutrons, and
Electrons

• Number of neutrons Mass Number Atomic Number
• Shorthand Notation Mass/Atomic Element
• OR Element Mass number
• Practice 9-12 Determine number of protons,
  electrons, and neutrons, completing tables of
  atomic number, mass number, protons, neutrons,
  electrons, symbol notation, Determining from
  symbol neutrons

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Today (Day 20)

• (0-5) Opener
• (5-15) Discuss HW
• (15-30) Quiz
• (30-43) Isotopes

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What are Isotopes?

• Atoms that have the same number of protons but
  different numbers of neutrons
• Different mass numbers
• Atoms are chemically alike behave similarly
• Common misconception radically different NO!
• Examples 3 isotopes of hydrogen
• Tritium Spiderman 2 errors MOVIE CLIP
• Gas, not solid
• More than 25 pounds in world
• Chemical symbols, Subatomic particles examples
  for isotopes (O-16,17,18)
• Symbolic Notation - isotopes

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Today (Day 21)

• (0-10) Opener/Discuss HW
• (10-15) Discuss QUIZ
• (15-20) Spiderman 2 Clip
• (20-30) Activity Isotope Numbers Relay Race
• (30-43) Average Atomic Mass
• (0-43) Isotopes and Atomic Mass Lab

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Opener - 9/29

• Determine the number of protons, neutrons, and
  electrons in the following isotopes
• Hydrogen-1, Hydrogen-2, and Hydrogen-3

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What is average atomic mass?

• Weighted grades analogy
• Masses of subatomic particles ridiculously small
  needed something more convenient
• Arbitrary amount set Carbon-12 atom 12.00000
  amu
• 1 amu (atomic mass unit) 1/12 mass of C-12 atom
• Mass of a single proton/neutron 1 amu
• Why are the masses decimals?
• Most elements exist as a mixture of 2 or more
  isotopes
• Look at average atomic masses of elements can
  you speculate which isotope is most common?

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How do you calculate average atomic mass?

• Average atomic mass weighted average mass of
  atoms in naturally occurring sample
• Number on Periodic Table explains why we could
  not use as mass number
• Reflects both the mass and the relative abundance
  of the isotopes as they occur in nature
• Calculating average atomic mass
• First, example of which is closer?
• Next, an example comparing to weighted average in
  class (grades)
• Finally, example using exact percentages and
  masses
• Finish HW/EC problems
• Practice 14,16

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Today (Day 22)

• Read Article
• Socratic Seminar

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Today (Day 24)

• Review

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Today (Day 25)

• Chapter 4 Test

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Origin of Periodic Table

• Mendeleev
• Listed elements in columns and in order of
  increasing atomic mass
• Elements in groups with similar properties
• Moseley
• Determined atomic numbers
• Rearranged periodic table to current state
• P-Tables Online
• HTML Table
• Interactive Periodic Table
• Comic Book P-Table

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Organization of Periodic Table

• Increasing atomic number
• Periods
• Horizontal rows
• Groups
• Vertical columns of elements
• Periodic law
• Repetition of chemical and physical properties
• Representative elements
• Metals (alkali, alkaline earth, transition)
• Nonmetals (halogens, noble gases)
• Metalloids