Chapter 5 The Periodic Table

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Chapter 5 The Periodic Table
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5.1

• Organizing the Elements

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Antoine Lavoisier

• In 1779 this French chemist categorized elements
  into four types
• Metals
• Non-metals
• Gases
• Earths
• For 80 years, scientists looked for a better
  organizing principle for all elements

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Dmitri Mendeleev

• This Russian chemist found the answer.
• Realized in the 1800s that there was a pattern
  to the elements.
• 63 known elements existed at the time.
• Wrote each elements name and properties on
  cards.

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Mendeleev

• Subatomic particles (protons, neutrons,
  electrons) had not been discovered.
• So he arranged according to the atomic mass.
• He arranged elements into rows in order of
  increasing mass so that elements with similar
  properties were in the same column.

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Problem with Mendeleevs Table

• Some heavier elements were placed ahead..
• .of lighter elements.

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What do the dashes represent? Why are masses
listed with some of the elements, but not with
all of them?
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• Mendeleev left blanks in his table for
  undiscovered elements.
• He knew what their properties would be and left
  locations or parking spots for them.
• Proof of a model being correct is whether or not
  it can be used to predict.
• The blanks in his table were eventually filled
  with elements whose properties he predicted.

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• He named undiscovered elements within a group
  after known elements within it.
• Eka-aluminum
• This is the name he gave to the element found
  just one spot below aluminum.
• He predicted its eka-aluminums properties based
  upon the trend within the rest of the group.
• It would be a soft metal with a low melting point
  and a density of 5.9 g/cm3.
• In 1875, a new metal with nearly these identical
  properties was discovered.
• Eka-aluminum then was said to be Gallium.
• 1st time that it proved useful and not the only
  time.

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5.2 The Modern Periodic Table

• Mendeleevs Periodic table arranged elements in
  order of increasing _________.
• His Periodic table pre-dates protons discovery.
• The modern Periodic table arranges elements in
  order of increasing __________.
• See p. 131. Why is the Modern Periodic table not
  shown in the book as it is on this page?

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PERIOD
ROW
C O L U M N
F A M I L Y
G R O U P
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• 18 columns or groups
• 7 rows or periods
• Periodic Law
• Properties of the elements are a function of
  their atomic number.
• The two bottom rows shown on the bottom of the
  Periodic table are called the Rare Earth
  elements.
• Lanthanide series named after Lanthanum.
• Actinide series named after Actinium.

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1
Atomic Number
H
Atomic symbol
Hydrogen
Element name
1.0079
Average Atomic Mass
The average atomic mass of an element is a
weighted average of all the isotopes of an
element. Every element has many different forms
with not any single form being more correct than
the other.
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• Atomic mass units
• amu
• Since a amu is 1/12 the mass of an isotope of
  C-12.
• Why C-12 ??? A very common atom and the most
  abundant isotope of carbon.
• The average atomic mass of an element is
  calculated by multiplying each of its isotopes
  abundance by its mass and then adding them all
  together.

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Classes of Elements

• Divided in 3 ways
• Physical state
• Solid
• Liquid
• Gas
• Natural or artificial
• Elements 1-92 occur naturally
• gt 92 are man-made
• Properties
• Metals
• Non-metals
• Metalloids

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Elements exist in 3 states -solids -liquids -g
ases Solids are represented in black. Liquids
are represented in purple. Gases are represented
in red.
Non-metals are represented with an orange square
Metals with a blue square and Metalloids with a
green square.
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• Metals
• Conduct heat __________
• Nearly always solid (except Hg)
• Malleable (aka bendable)
• Ductile (can be drawn into a thin wire)
• Some very reactive
• Transition metals
• Groups 3 12
• Some of the 1st elements found were from this
  group.
• Form brightly colored compounds

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• Non-metals
• Properties are the opposite of those of metals.
• Non-metals can be found in all 3 phases.
• Some non-metals are very reactive while others
  are not.
• Metalloids
• Show a combination of the properties of metals
  and non-metals.

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• Variation across a period
• Elements are most metallic on the left and become
  less as move to the right.
• More non-metallic on the right.
• Metallic -------gt--------------gt-----------------
  gt Non-metallic
• The metals in Group 1 are the most reactive of
  all metals.
• The non-metals in Group 17 are the most reactive
  of all non-metals.

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5.3 Representative Elements

• Periodic Table labeled in 2 ways
• 1A 8A 1B-10B
• 1 -18
• The As are a reminder that the before it
  equals the of valence e- for its group.
• Group 1A elements have 1 valence electron.
• Valence electrons are those found the greatest
  distance away from the nucleus.

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• Elements in the same family have similar
  properties because they have the same number of
  valence electrons.

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Alkali metals

• ? valence electron in each.
• Extremely reactive, _____ metals.
• Always found in nature combined with other
  elements.
• Elements at the top of this group are less
  reactive than those at the bottom.
• Hydrogen is found here, but isnt really a real
  member.

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Alkaline Earth Metals

• ? valence electrons
• Harder than alkali metals.
• Less reactive than alkali metals.
• Be is not reactive Ca, Ba, Sr react w/ cold H2O
  Mg reacts only with hot water.
• Mg Ca are important for our health.

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Boron family

• ? valence electrons
• Named after 1st element in family.
• All its elements have ? valence electrons.
• Aluminum best known of family.
• Most abundant metal in Earths crust.
• Very light, strong metal.
• Boron (B) is a metalloid the others _____.

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Carbon group

• 4 valence electrons
• 1 non-metal (___________)
• 2 metalloids (__________ __________)
• 2 metals (________ ________)
• Carbon is the life element.
• Silicon is the 2nd most abundant element in the
  crust of planet.

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Nitrogen family

• 5 valence electrons
• 2 non-metals (______ ______)
• 2 metalloids (_______ _______)
• 1 metal (_____)
• Nitrogen makes-up 78 of air.
• Human body fertilizers
• Phosphorus has multiple allotropes.
• White phosphorus is dangerous illegal military
  weapon.
• Red phosphorus used in match heads.

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Oxygen family

• ? valence electrons
• 3 non-metals (______, ______ ______)
• 2 metalloids (______ ______)
• Oxygen is the most abundant element in the
  Earths crust.
• 21 of all air is oxygen.

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Halogens

• ? valence electrons
• Halogen means salt forming.
• __non-metals __ metalloid
• Most reactive non-metals.
• Just as reactive as Alkali metals.
• Fluorine is the most reactive
• Top elements most reactive, bottom least.

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Noble gases

• Aka Inert gases
• ? Valence electrons (except He)
• Colorless
• Odorless
• Very un-reactive
• Many of them have industrial uses.