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PERIODIC TRENDS STUDY GUIDE
“THE HOW, THE WHY AND THE WHAT…”
HOW THEY TREND….
PERIOD TRENDS
Decrease from left to right
Increase from left to right
Generally increase across
a period
ATOMIC RADII
IONIZATION ENERGIES
ELECTRONEGATIVITY
GROUP TRENDS
Increase from top to bottom
Decrease from top to bottom
Decrease down a group or remain about
the same
WHAT THE TRENDS ARE (IS)….
ATOMIC RADII
IONIZATION ENERGIES
ELECTRONEGATIVITY
DEFINED AS…
The distance (in pm) from the nucleus to the outermost electron orbit or one-half the distance between
the nuclei of identical atoms that are bonded together.
Which element, Lithium or Neon, has the largest
atomic radius?
The energy required to remove one electron from a
neutral atom of an element. Ionization is any process
that results in the formation of an ion. An ion is an
atom that has either a positive(cation) or a
negative(anion) charge as a result of a loss or a gain of
electrons. Has a cation lost or gained electrons? An
anion?
A measure of the ability of an atom in a chemical
compound to attract electrons from another atom in
the compound. What is the most electronegative
element?
WHY THEY TREND THE WAY THEY DO…
PERIOD TRENDS
Increasing nuclear charge
GROUP TRENDS
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ATOMIC RADII
IONIZATION ENERGIES
ELECTRONEGATIVITY
or more protons are added
to the atom causing the
nuclear pull on the
electrons to increase..
Because as the atom
becomes increasingly more
like a noble gas electron
configuration (or achieves
noble gas stability), it
requires more energy to
ionize a neutral atom of that
element.
See below
More sublevels are added to the atom,
(1s, 2s, 3s, etc…).
Because of shielding and because the
electrons are in higher energy levels and
thus are further from the positive nuclear
pull. Therefore, it requires less energy to
ionize a neutral atom as one trends from
top to bottom down a group. Shielding
occurs when more electrons lie between
the nucleus and the electrons in the
highest occupied energy levels.
See below
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ATOMIC RADII
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