Transcript Periodic Trends

Atomic Structure and
Periodicity
Periodic Trends
Ionization Energy
 An
electron can be removed from an
atom if enough energy is absorbed (+)
 Ionization energy – the energy
required to remove one electron from
a gaseous neutral atom
A (g) + energy  A+ (g) + e measurements of this are made on
individual atoms in gas phase to avoid
interactions with nearby atoms
Ionization Energy
Ionization Energy
 if
one electron is removed, the
positive charge binds the electrons
more tightly so 2nd ionization energy
must be higher
 the largest jump in energy is when you
remove a core electron instead of
valence
Ionization Energy
Ionization Energy

Across Period:


requires more
energy to remove
an electron so
increases
because electrons
added in the same
energy level do not
shield electrons
from nuclear
charge

Down Group:


requires less
energy to remove
electron so
decreases
because the
valence electrons
are farther away
from protons
attracting them
Ionization Energy
Ionization Energy
Electron Affinity
Electron Affinity – the energy change
when an electron is added to a
gaseous neutral atom

exothermic (-)
A + e-  A- + energy
Electron Affinity

Across Period:


releases more
energy so number
increases (gets
more negative)
because electrons
added in the same
energy level do not
shield electrons
from nuclear
charge

Down Group:


releases less
energy so number
decreases (gets
less negative)
because the
electrons being
added are farther
away from the
attracting protons
Electron Affinity
Atomic Radii
 Defined
by the edge of
its orbital but since the
edges are fuzzy,
difficult to determine
 Atomic Radii – half the
distance between the
nuclei of identical
atoms that are bonded
together
Atomic Radii

Across Period:



atoms get smaller
because of the
increased number of
protons attracting the
electrons
the electrons added
in the same energy
level do not shield
electrons from
nuclear charge

Down Group:



atoms get larger
increases
because the energy
levels being added
to the atom
Atomic/Ionic Radii