Ionisation energies

first ionisation energy

the energy required to remove the first electron to make an atom ionised.

ionisation energy

the energy required to remove a mole of electrons from a mole of atoms in the gaseous state. measured in KJmol^-1.

second ionisation energy

the second electron needs more energy than the first electron as the second electron is being removed from a 1+ ion

third ionisation energy

the third electron needs more energy to be removed as it is being removed from a 2+ ion

the lower the ionisation energy..

the easier it is to form a positive ion

what are the factors affecting ionisation energy

nuclear charge, distance from nucleus and shielding

how does nuclear charge affect ionisation energy

the more protons a nucleus has, the more positively charged it is and the stronger the attraction for the electrons

how does distance from nucleus affect ionisation energy

an electron close to the nucleus will be much more strongly attracted than an electron further away.

how does shielding affect ionisation energy

as the number of electrons between the outer electron and the nucleus increases. the outer electron feels less attraction to the nucleus.

ionisation energies increase across a period..

because the nuclear charge is increasing and this makes it more difficult to remove an electron

what makes it easier to remove electrons

the repulsion between paired electrons

why does the ionisation energies decrease down a group

because of the inner electrons shielding the nuclear charge and the outer electron gets further away from the nucleus as you go down the group.

large increases occur when there is a change of shell, why?

because there is a big decrease in shielding

energies are always greater than the previous one, why?

the elctron is being pulled away from a positive species