Transcript Notes #3

Chemistry
Chapter 6/7
Notes #3
Periodic Trends

Many elemental properties change in a
predictable way (trend) as you move across
the periodic table in periods, or down the
periodic table in families/groups
 4 Examples
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Atomic Radius
Ionic Radius
Ionization Energy
Electro negativity
Atomic Radius

Going left to right on the periodic table atomic
radius decreases
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Due to increased nuclear positive charge, pulling
electrons closer
Going down the periodic table (in columns)
atomic radius increases

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Due to increasing p.e.l.’s
E- are further from nucleus – hence less pull on
them
Shielding
Atomic Radius
Ionic Radius

Ion – Atom that has lost or gained electrons
and has an overall charge

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Loss of electrons = positive charge
Gain electrons = negative charge
Loss of e- : gets smaller than original atom
(empty outer energy level – electrons get
pulled closer to nucleus)
 Gain of electrons: Radius gets bigger –
increases electrostatic repulsion (likes repel)
Ionic Radius

Moving down the columns
Ionic radius generally increases
 Same reason that atomic radius increases
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
Moving left to right

Generally decreases.
 First along the metals
 Big jump in size when you hit nonmetals
 Then, they decrease again
Ionic Radius
Ionic Radius
Ionic radius decreases
Ionic radius increases
Ionization Energy

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The energy needed to overcome the attraction
between the + charge in the nucleus and the –
charge of the electron in order for an electron to be
removed from the outer energy level of a neutral
atom
High ionization energy: atom has strong hold on its
eLow ionization energy – atom loses e- more easily
 All follows the octet rule!
Moving down the columns it decreases (atoms are
larger – the electrons are farther from the nucleus –
so they are easier to remove)
 Moving left to right – atoms have a stronger hold
on their electrons
Ionization Energy
Ionization energy increases as you move to
the right
Ionization energy
decreases
Electro negativity
The ability of an atom to attract electrons
in a chemical bond
 Moving left to right – it increases
 Moving down the columns, it decreases

Lowest electro negativities are found at
the lower left of the table
 F = most electronegative element

Electro negativity
Electronegativity increases as you move to the right
Electronegativity
decreases