Slides in this set
The first ionisation energy of an element is the energy required to remove one electron
from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.
Successive Ionisation energies are a measure of the energy required to remove each
electron in turn.
First Ionisation energy of sodium Na (g) Na+ (g) + e-
Factors effecting ionisation energies
· The greater the atomic radius the smaller the nuclear attraction experienced by the outer shell
electrons, making it easier to remove one electron from the outer shell
· As the number of inner shells increases, the effect of electron shielding increases, decreasing the
nuclear attraction for outer shell electrons making it easier to remove one electron from the outer
· The greater the nuclear charge the greater the attractive force on the outer shell electrons making
it harder to remove one electron from the outer shell.…read more
Shells and Orbitals
1st Shell 2
2nd Shell 8
3rd Shell 18
4th shell 32
An atomic orbital is a region within an atom that can hold up to two electrons
with opposite spins.
Sub shell Number of Number of Electron configuration
Orbitals electrons Krypton
s 1 2 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6
p 3 6 A sub shell is a group of the same type
d 5 10 of Atomic Orbitals (a, p, d or f)…read more
Filling the shells
Shells are filled by increasing orbital
energy order, However;
·The 4s sub shell has a lower energy
than the 3d sub shell.
·The 4s orbital fills before the 3d
·The 4p orbital fills after the 3d
orbital is full.
·When positive ions are formed,
electrons are removed from the highest
·When negative ions are formed
electrons are added to the highest energy
Again 4s an exception it is filled before 3d
and so emptied before 3d when positive
ions are formed.…read more