PERIODICITY
The periodic table and physical properties
Periodic Properties
•Elements show gradual changes in certain physical
properties as one moves across a period or down a group
in the periodic table.
•These properties repeat after certain intervals. In other
words they are PERIODIC.
•Periodic properties include:
•Ionization Energy
•Atomic Radii
•Ionic Radii
•Electronegativity
•Electron Affinity
TRENDS IN
IONIZATION
ENERGY
Ionization energy:
The energy required to remove each outermost electron from one mole of atoms or
ions of an element in the gaseous state is known as the ionization energy.
Largest toward upper right corner of periodic table since these atoms hold on to their
valence electron the tightest.
•Using relevant data from the data booklet, use
excel to create graphs for the following data:
•First ionization energy down group 1, and
•First ionization energy across period 3.
•Using the graphs obtained, describe and explain
the trends observed.
Activity
1st I.E. down group 1
•Down a group, the 1st
I.E. decreases.
•The outer electron to be
removed is in a higher
principal energy level.
•It is further away from
the attraction of the
nucleus.
•Thus, less energy is
needed to remove the
electron from the atom.
0
100
200
300
400
500
600
lithium sodium potassium rubi dium caesium
first ionization energy/kJ
mol-1
1st I.E. across period 3
•Across a period, the 1st I.E.
generally increases.
•There are more protons in
each nucleus so the nuclear
charge in each element
increases.
•Therefore the force of
attraction between the
nucleus and outer electron is
increased.
•There is a negligible increase
in shielding because each
successive electron enters
the same energy level.
•More energy is needed to
remove the outer electron.
0
200
400
600
800
1000
1200
1400
1600
sodium
magnesium
aluminium
silicon
phosphorus
sulfur
chlorine
argon
first ionization energy/kJ
mol-1
1st I.E. across period 3
•However, there are
discontinuities in the
general trend:
•1st I.E. decreases from Mg
to Al.
•Electronic configuration of
Mg:
•[Ne] 3s2
800
1000
1200
1400
1600
first ionization energy/kJ
mol-1
