Periodic Table

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Periodic Table

• Chemistrys Best Friend!

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History of the PT

• "The properties of the elements are a periodic
  function of their atomic masses. Dimitri
  Mendeleev
• Mendeleev was partially successful in arranging
  the elements into a chart that allowed the
  prediction of properties.
• He arranged the known elements in the 1870s
  according to increasing atomic masses.

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History of PT

• In 1914, Prof Moseley, a British Physicist,
  rearranged the elements and cleared up the
  contradictions and Mendeleev's inconsistencies.
  How?
• Moseley based his arrangement on atomic numbers
  and not atomic masses.

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History of the PT

• Moseley's periodic law is now considered the
  current Periodic Law!
• The elements are arranged in vertical columns
  known as Groups.
• The horizontal rows of elements are referred to
  as "periods"

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Many Styles to Choose From!

• http//chemlab.pc.maricopa.edu/periodic/styles.htm
  l

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Groups

• The elements of the periodic table can be
  classified into three main groups
• metals
• semimetals or metalloids
• nonmetals

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Metals

• Metals are generally malleable (easily shaped),
  ductile (easily pulled into wire), good
  conductors, and lustrous

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Nonmetals

• Nonmetals are generally brittle and poor
  conductors. Their other characteristics vary more
  than those of metals.

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Metalloids

• Semimetals or metalloids possess characteristics
  of both metals and nonmetals. Semimetals may act
  as either metals or nonmetals, depending on the
  situation.

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General Trends
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Atomic number, atomic mass, and density

• Atomic number, atomic mass, and density increase
  as you go down a family (or group).
• Atomic number, atomic mass, and density increase
  as you go across a period.

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Atomic Radii
The atoms radii shown are in picometers (pm
10-12 m).
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Explaining the Radii Trend

• Along a period (left to right) the atomic number
  increases while the valence electrons remain in
  the same shell.
• Due to the increasing nuclear charge (pulling
  electrons closer to the nucleus) the radii of the
  atoms decrease from left to right.

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Explaining the Radii Trend

• Down a group as the atomic number increases the
  shells filled increase (1s, 2s, 3s, etc.).
• Because the atomic orbitals for each successive
  shell get larger and larger the atomic radii
  increase from top to bottom along a group.
• Increased size more than compensates for any
  increased nuclear charge.

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Ionization Energy

• Energy required to remove an electron from a
  gaseous atom
• Ionization energy increases as you go across a
  period
• The nucleus has a greater attraction for the
  electrons
• Ionization energy decreases as you go down a
  family
• The outermost electron is further from the
  nucleus because the atom is larger and is
  therefore easier to remove.

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Electronegativity

• What does this mean?
• It is the tendency for an atom of one kind of
  element in compound to attract the electrons from
  the other atom in the compound.
• For example In HCl, the chlorine atom has a
  greater attraction for the electron from the
  hydrogen atom than the hydrogen atom does.
  Remember, Cl wants one more electron to fill the
  3p sublevel. Therefore, Cl has a higher
  electronegative value than H.

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Electronegativity Trend

• Across a period electronegativity increases
  because nonmetals need to gain electrons to fill
  s and p sublevels
• Down a family electronegativity decreases
  because metals would rather lose electrons to
  have filled s and p sublevels

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Electron Affinity

• Electron affinity is an atoms ability to
  attract and hold onto an electron.
• Strongest toward RIGHT of PT.
• Decreases somewhat DOWN a group.

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Explaining the Ionic Size Trend

• Positive ions are smaller than the atoms they
  come from.
• Sodium is 2,8,1 Na is 2,8. You've lost a whole
  layer of electrons, and the remaining 10
  electrons are being pulled in by the full force
  of 11 protons.

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Explaining the Ionic Size Trend

• Negative ions are bigger than the atoms they
  come from.
• Chlorine is 2,8,7 Cl- is 2,8,8. Although the
  electrons are still all in the 3-level, the extra
  repulsion produced by the incoming electron
  causes the atom to expand. There are still only
  17 protons, but they are now having to hold 18
  electrons.

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What is shielding?What is the trend?

• Shielding is a protection.
• The outermost electrons are protected from the
  positive nuclear attraction by the inner
  electrons the outermost electrons do not feel
  such a strong pull by the nucleus.
• Shielding is constant across a period because the
  number of inner electrons stays the same.
• Shielding increases down a family because there
  are more inner electrons.

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So what?

• Shielding helps explain trends in atomic radius,
  ionization potential and ionic size.

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Melting point, boiling point, Heat of fusion,
Heat of vaporization

• Decrease as you go down on the left side of the
  table.
• Increase as you go down on the right side of the
  table after the nitrogen family.
• No trend for going across a period.
• Ignore transition metals.

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Meet the Main Group Elements!

• Or Who are the Elements in Your Neighborhood?
• http//members.tripod.com/Tiny_Dancer/peopleinyour
  neighborhood.mp3

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What Are All The Groups?
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Groups Can Be a Family Affair

• There are also other, less specific, groups of
  elements. These groups are all over the table.
• Scientists group these families of elements by
  their chemical properties. Each family reacts a
  different way with the outside world.
• Sometimes families align with the columns or
  groups, sometimes they dont. Only tests will
  tell for sure!

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Alkali Metals

• One electron in their outer (valence) electronic
  shell
• Tend to lose a single electron to form a 1
  charged positive ions
• Highly reactive!
• Combine with negatively charged ions to form
  salts
• Soft and easily cut
• Low densities melt at low temperatures.

Because they are so reactive,alkali metals are
alwaysfound in compounds.
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Alkaline Earth Metals

• Two electrons in outer shell
• Tend to lose two electrons to form 2 positive
  ions
• Also very reactive
• Sometimes they bond with two halogen atoms (BeF2)
  and sometimes they form one double bond (CaO)
• Called alkaline because they are likely to form
  solutions with a pH greater than 7 (bases).

Alkaline earth metals are a major part of seas
shells andmagnesium (mag) wheels.
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Boron Group

• Three electrons in outer shell
• Tend to lose three electrons to form 3 positive
  ions
• Boron is a metalloid. Others in group are metals.
• Boron and Aluminum have widespread commercial
  applications

Aluminum is used to makebaseball bats. Your body
heatwill melt Gallium.
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Carbon Group

• Four electrons in outer (valence) shell
• Tend to share these four electrons to form
  covalent compounds
• Carbon can form an unlimited number of compounds.
• Most compounds in living things contain carbon.

Carbon makes up graphite,an excellent lubricant.
Siliconis a major part of many minerals.
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Nitrogen Group

• Five electrons in their outer (valence) shell
• Tend to gain three electrons to form 3- charged
  negative ions
• 80 of our air is Nitrogen (living things need
  Nitrogen to make proteins).

Phosphorus is used to makematches. Liquid
Nitrogen willinstantly freeze a rose.
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Oxygen Group

• Six electrons in outer (valence) shell
• Tend to gain two electrons to form 2- negative
  ions
• Oxygen is the most important and most abundant
  element on Earth!
• Plants produce oxygen during photosynthesis

Astronauts rely on oxygentanks to breathe.
Sulfur is ayellowish non-metal solid.
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Halogens

• Chemically reactive!
• Not all halogens react with the same intensity.
  Fluorine is the most reactive and combines all of
  the time. As you move down the column, reactivity
  decreases.
• When a halogen combines with another element, the
  resulting compound is called a halide.

Salt and plastics bothcontain halogen
compoundsor halides.
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Noble Gases

• Eight electrons in their outer (valence) shell
• They are chemically inert and do not combine with
  other elements
• They do not lose, gain, or share electrons
• All Noble Gases exist in the earths atmosphere

Helium makes blimps floatand other gases create
thecolors in Neon lights.
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Transition Metals

• Numbers of electrons lost or gained varies
• Much less reactive than alkali and alkaline earth
  metals
• Often found in ores (minerals)
• Good conductors of heat and electricity

Transition metals make up most metal objects.
Some form colorfulcompounds.
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Rare-Earth Metals

• Also called Lanthanides
• Except for Promethium, all Lanthanides occur in
  nature
• Pure Lanthanides look like steel and have
  steel-like properties
• Tiny amounts of pure Lanthanides are used in
  Lasers

Rare earth metals have properties that make them
useful in certain special devices.
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Actinides

• Most are synthetic and are made in laboratories.
  Only Actinium, Thorium, Protactinium Uranium
  occur naturally
• All isotopes of all the actinides are radioactive
• Actinide metals tarnish readily in air
• React with boiling water or dilute acid to
  release hydrogen gas

All isotopes of actinides are radioactive. Most
are synthetic.
Learn more http//www.ucc.ie/ucc/depts/chem/dolch
em/html/elem/group.html
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Class Project We are going to create a Periodic
Table of you!

• Step One Complete the survey to help identify
  your main characteristics
• Step Two Group like students into families
• Step Three Create a giant PT with each student!

http//www.chemsoc.org/viselements/pages/pertable_
fla.htm