Ionisation Energy

Seite 1

1st ionisation energy: The energy required to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 moles of gaseous 1+ ions

2nd ionisation energy: The energy required to remove 1 electron from each atom in 1 mole of gaseous singly charged ions to form 1 mole of gaseous ions with 2+ charges

Nuclear charge: more protons in the nucleus, the higher the nuclear charge (and therefore number of protons)

Nuclear attraction: the further away the outer shell is, the weaker the attraction to the nucleus

Shielding: the more shells = the more shielding

Atomic radius: Group - increases as you go down

Period - decreases as you go across (this is because the shielding is the same but the pull is increased due to the ionisation energy

Going down a group:

Ionisation energy: decreases - easier for the electrons to be lost

Atomic radius: increases - outer electrons are further away from the nucleus and the distance between the outer electrons and nucleus increases

Shielding: increases - because an extra shell of electrons is added each time

Nuclear attraction: - weaker between the outer electron and nucleus

Therefore t is easier for an outer electron to be lost

Nuclear charge - increases (even though the ionisation energy decreases)

Across a period:

Ionisation energy: increases

Atomic radium: decreases - the nuclear charge increases as a proton is added each time you move across while the shielding stays the same

Nuclear attraction: stronger - outer electrons are closer to the nucleus (as the atomic radius has decreased)

Therefore it is harder to loose and electron

Period 3

There is a drop in energy from Mg to Al:

Electrons are being removed from the p orbital not the s orbital, the p orbital being slightly further away from the nucleus so the electrons within that orbital are slightly easier to remove

There is a slight drop from P to S

The P orbital has 3 main orbitals, for Phosphorus each has one electron it itself

For Sulphur it has two electrons in the first orbital and then one each in the other two, the two electrons in the first orbital increase the repulsion slightly making it easier for the electrons to be removed

Successive ionisation energy

This is shown on a table, with the ionisation energy on the Y axis and the 1st, 2nd, 3rd, 4th ect ionisation of electrons being lost for the X axis.

This 1st is always the outer most shell of the element undergoing ionisation as it is the first to be removed.

Small jumps represent a change in orbitals while larger jumps suggest a change in shell, this is due to the energy needed to remove the electrons which now have a slightly harder pull as they are closer to the nucleus