PS 101

1
PS 101

• Kim Cohn
• Email address
• Kcohn_at_academic.csubak.edu

2
Comments- Demo

• What evidence do you have that when magnesium is
  heated in air that a chemical change occurs?
• Was it a good idea or a bad idea to make car
  wheels out of magnesium?

3
Organizing the Elements

• Can be arranged by atomic number or atomic mass.
• 1, 2, 3, 4, 5, 6, etc.
• 1.008, 4.003, 6.941, etc.
• Can be arranged by physical or chemical
  properties.
• Radius of atom, ionization potential etc.
• See page 387.

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Page 387 The Periodic Table
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Organizing the Elements - 2

• The atomic mass is usually placed under the
  symbol for the atom.
• The periodic table is arranged by atomic number
  1, 2, 3, 4, etc., with new rows placed when there
  is a big change in a property.

Atomic Number
6
C
Atomic Mass
12.0
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Page 387 The Periodic Table
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Organizing the Elements - 3

• As you go down a column (group), size goes up.
• As you go down a column (group), ionization
  potential (the energy needed to remove and
  electron) goes down.
• As you go across a row the ionization potential
  goes up.

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Page 387 The Periodic Table
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Metals, Nonmetals, Metalloids

• The broken line represents the boundary between
  metals and nonmetals.
• To the right of the broken line, nonmetals.
• To the left of the broken line, metals.
• Next to the broken line on the right are the
  metalloids.

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Page 387 The Periodic Table
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Metals, Nonmetals, Metalloids - 2

• Some of the groups (columns) have names.
• Group 1 Alkali metals.
• Group 2 Alkali earths.
• Group 17 Halogens.
• Group 18 Noble Gases.
• Groups 3 to 12 Transition Metals.

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Page 387 The Periodic Table
13
Noble Gas Shells

• 1st shell can hold 2 electrons Helium.
• 2nd shell can hold 8 electrons Neon.
• 3rd shell can hold 8 electrons Argon.

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Page 387 The Periodic Table
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Noble Gas Shells 2

• The electrons that are outside the noble gas
  configuration are the ones that are responsible
  for the chemistry of the element.
• Hydrogen has one electron outside of its noble
  gas configuration.
• It would like one more.
• Consider Na and Cl.

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Page 387 The Periodic Table
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Noble Gas Shells - 3

• Na has 11 protons and 11 electrons.
• The nearest noble gas, neon, has 10 protons and
  10 electrons.
• What does Na need to do to acquire a noble gas
  configuration?
• What does Cl need to do?

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Page 387 The Periodic Table
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Periodic Trends Size

• As you go across the periodic table the number of
  protons ( charge goes up).
• As you go across the table, the electrons are all
  found in the same shell.
• The increase in positive charge pulls in the
  electrons so the atoms get smaller as you go
  across.

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Periodic Trends Size

• As you go down the periodic table the number of
  protons ( charge goes up).
• As you go down the table, the outer electrons are
  found in new shells that are further away than
  the previous shell.
• The increase in size of the shell makes the atoms
  get larger as you go down.

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Periodic Trends Ionization Potential

• Ionization potential is a measure of how hard it
  is to remove an electron.
• As you go across the periodic table the number of
  protons ( charge goes up).
• As you go across the table, the electrons are all
  found in the same shell.
• The increase in positive charge pulls in the
  electrons so the ionization goes
• Up as you go across.

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Periodic Trends Ionization Potential

• As you go down the periodic table the number of
  protons ( charge goes up) but the size goes up.
• These are two competing trends.
• The trend that is more important is the increase
  in size.
• Therefore as you go down, the ionization goes
• Down.

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Question

• Why is the ionization potential for Rb less than
  that of Na?
• Which is a larger atom, Na or Li?
• Which is a smaller atom, Na or Cs?