electron configuration

• Ionisation energy: The energy required to remove a mole of electrons From a mole of atoms in gaseous state.
• Ionisation energy is measured in kJ mol^-1.
• The first electron requires the least amount of energy to remove because it is being removed from a neutral atom, this is known as the first ionisation energy.
• The second electron needs more energy than the first one because it is being removed from a 1+ ion, this is known as the second ionisation energy.
• The third electron needs even more energy to be removed because it is being removed from a 2+ ion, this is known as the third ionisation energy.
• Each main energy level can hold a maximum number of electrons given by the formula 2n^2 where n is the number of the main level.
• The first main energy level only contains an s-sub-level.
• Electrons in different shells have different amounts of energy.
• The outer electron in the main level gets further from the nucleus in each case as you go down a group in the periodic table.
• There is a general decrease in first ionisation energy going down the group in the periodic table.
• Charge is increasing making it harder to remove an electron.
• Going down a group in the periodic table, the nuclear charge increases, and the actual charge felt by the electron in the outer shell is less than the full nuclear charge due to the effect of the inner electrons shielding the nuclear charge.
• The main energy levels are divided into sublevels called s, p, d & f.
• The fourth electron needs even more energy to be removed, and so on.
• Successive ionisation energy is the term used to describe the process of removing electrons one by one from an atom, starting with the outer electrons and working inwards.
• Ionisation energy generally increase across a period because the nuclear charge increases.