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Periodic Trends


Periodic Trends Can Studying Chemistry Be Trendy? As you look at the periodic table and focus in on the elements and their characteristics, you can see there are ... – PowerPoint PPT presentation

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Title: Periodic Trends

Periodic Trends
Can Studying Chemistry Be Trendy?
  • As you look at the periodic table and focus in on
    the elements and their characteristics, you can
    see there are noticeable patterns (trends) that
    go across a period (horizontal row) on the
    periodic table.
  • These quantitative (able to measured with numbers
    and units) characteristics that follow distinct
    patterns across the periodic table are called
    periodic trends.
  • RememberMendeleev didnt get all the fame and
    fortune for nothing he was crazy smart!
  • The periodic trends that we will be studying are
  • Atomic Radius
  • Ionization Energy
  • Electron Affinity
  • Electronegativity

Atomic Radius
  • The atomic radius of an element is an estimate of
    the size of an atom from its nucleus to its outer
  • The Trend of Atomic Radius
  • Atomic radius gets smaller as you move left to
    right on the periodic table.
  • As you go across a row, you add more protons to
    the nucleus and more electrons to the orbits
    this means more attraction between the opposing
    charges and the orbits are pulled in even closer
    to the nucleus.
  • Atomic radius gets larger as you go top to bottom
    on the periodic table.
  • Each time you go down a spot on one of the
    columns on the periodic table, you are adding
    another orbit this additional orbit increases
    the size of the atom.
  • Understanding atomic radius will actually help us
    understand some of the other periodic trends.

Atomic Radius
Ionization Energy
  • The trend of ionization energy deals with ions
    atoms that have lost or gained electrons. (Anions
    are negative ions cations are positive ions).
  • Ionization energy is the energy needed to remove
    an electron from a gaseous atom.
  • The Trend of Ionization Energy
  • Ionization energy increases as you go left to
    right on the periodic table.
  • As you go let to right, the radius of the atom is
    smaller because of the greater attraction between
    the protons and electrons. The electrons are
    being held more tightly and closely by the
    nucleus. You have to fight to get one free.
  • Ionization energy gets weaker as you move down a
    column on the periodic table.
  • As you go down a column, you add another orbit so
    the negative electrons are further away from the
    positive protons and the attractive force between
    them is not as strong. Its easier for anyone to
    come by an rip off an electron.

Multiple Ionization Energies
  • The term multiple ionization energies refers to
    the taking of more than one electron from a
    gaseous atom.
  • The trend here is that it gets a lot tougher to
    take more and more electrons from an atom.
  • The first electron taken will seem easy compared
    to the second. The second electron will be
    tougher than the first, but, will come away
    easier than the third and so on
  • As an electron is taken away, the protons are
    acting on fewer electrons and can pull them in
    even tighter.

Ionization Energy
Electron Affinity
  • Electron affinity is the energy released when an
    electron is added to a gaseous atom.
  • There is no clear pattern for the periodic trend
    of electron affinity although there tends to be a
    general increase in electron affinity as you go
    from the left to the right on the periodic table.
  • Note that you must spend energy to rip an
    electron off of an atom and energy is released,
    or given off, when an electron in added to an

Electron Affinity
  • Electronegativity is the relative strength of
    attraction an atom has for electrons while it is
    in a chemical bond.
  • Remember that chemical bonds can involve the
    sharing of pairs of electrons. The atoms are
    literally fighting to gain possession of those
    electrons the amount electron-grabbing muscle
    they have is called electronegativity.
  • The Trend of Electronegativity
  • Electronegativity increases as you go left to
    right across the periodic table.
  • There are more protons in the atoms as you go
    across the periodic table and this means there is
    more positive charge to attract the negative
  • Electronegativity decreases as you go down a
    column on the periodic table.
  • You are adding more orbits so the electrons are
    further away from the protons and there is less
    attractive force to grab the electrons.