Decreases in size the further to the
right the element is along a period
due to there being a larger positive
charge in the atoms nuclei
Increases in size the further
down a group an element is, as
there are more electronic shells
in elements further down the group
Ionic radius
Anions (Ions with a negative charge)
have a larger radii than their atoms
counterparts due to them having a
larger negative charge, making the
attraction to the nuclei weaker
Cations (Ions with a positive charge)
have a smaller radii than their atom
counterparts due to them having a
larger positive charge, making the
attraction to the nuclei stronger
Ionisation energy
Ionisation energy increases
the further the element is
to the right in a period
because the nuclear charge
increases, attracting the
negative electrons more to
the positive nuclei, The
atomic radii decreases,
therefore the electrons are
closer and more electrons
are added to the same shell.
Ionisation decreases the further an
element is down a group because;
The atomic radii decreases, therefore
the electrons are further away; The
nuclear charge increases but the
electrons are further away so there is
a weaker attraction; and the
electrons in lower shells block
attraction causing electron shielding
Anomalies to this rule:
1. Boron has a lower IE than
Beryllium because the 2p electrons
are slightly higher in energy than the
2s electrons and so the ionisation for
Boron is lower than for Beryllium
(Moving from an S shell to a P shell
lowers the IE)
2. Oxygen has a lower IE than Nitrogen because
the Px, Py and Pz only contain one electron. The
extra electron in Oxygen causes a pair and
repulsion making it easier to remove, hence
giving it a lower IE than Nitrogen (When the
P-shell has one electron in all 3 orbitals, the next
electron [4p^4] will have a lower IE due to that
fourth electron being easier to remove)
Electron Affinity
The energy released when 1 mole of
electrons is attached to one mole of neutral
atoms or molecules in the gas phase
X(g) + e- ===> X-(g)
Electronegativity
In general, the
electronegativity
increases the further
to the right in a period
the element is, and
decreases the further
down a group it is.
Electronegativity is the
tendency of an atom to attract
a shared pair of electrons
towards itself. An atom's
electronegativity is affected by
both its atomic number and
the distance at which its
valence electrons reside from
the charged nucleus.