What is ionisation energy?
The minimum energy required to remove 1 mole of electrons from 1 mole of a gaseous element
What factors affect ionisation energy?
Shielding
Nuclear charge
Atomic radius
How does shielding affect ionisation energy?
Decreases ionisation energy
More complete inner shells between the nucleus and the outer electrons, so nuclear attraction decreases, less energy is required to lose electron
How does nuclear charge affect ionisation energy?
Increases ionisation energy
Higher charge (more protons) = greater nuclear attraction, so more energy is required to lose electron
How does atomic radius affect ionisation energy?
Decreases ionisation energy
More complete inner shells means the force of attraction is weaker, and it is easier to lose an outer electron
How are elements arranged in the periodic table?
By atomic number
Why do isotopes of the same element have the same chemical properties?
Because they have the same electron configuration
What is the trend for ionisation energy across a period and why?
Nuclear charge increases
Atomic radius decreases
Nuclear attraction increases
THEREFORE: Ionisation energy increases
How can you tell what group an element is in by its successive ionisation energies?
Greatest difference in ionisation energy
If it’s between 2nd and 3rd, the element is in group 2
Why is the 2nd ionisation energy greater than the 1st for group 2?
Because the electron is not paired so there is no repulsion from the other electron
Meaning nuclear attraction increases, making it harder to lose the outer electron
Why does ionisation energy increase between shells?
Because the shells are closer to the nucleus, so nuclear attraction is greater and the electron is harder to remove
What is the trend for ionisation energy going down a group and why?
Atomic radius increases
Shielding increases
Nuclear attraction decreases
THEREFORE: ionisation energy decreases
