Notes on Ionisation Energy:

1. Ionisation energy is the energy required to remove an electron from an atom or ion in the gaseous state.
2. It is measured in kilojoules per mole (kJ/mol).
3. Ionisation energy can be classified into two types: first ionisation energy and successive ionisation energies.

First Ionisation Energy: 1. First ionisation energy is the energy required to remove the outermost electron from an atom in its gaseous state. 2. It is generally represented by the equation: X(g) → X+(g) + e- 3. The first ionisation energy generally decreases down a group and increases across a period on the periodic table. 4. This is due to the increasing nuclear charge and decreasing atomic radius across a period.

Successive Ionisation Energies: 1. Successive ionisation energies are the energies required to remove subsequent electrons from an atom or ion. 2. The second ionisation energy is always greater than the first ionisation energy, and so on. 3. This is because removing an electron from a positively charged ion requires more energy than removing it from a neutral atom.

Factors Influencing Ionisation Energy: 1. Nuclear charge: The greater the nuclear charge, the stronger the attraction between the nucleus and the electrons, resulting in higher ionisation energy. 2. Atomic radius: The smaller the atomic radius, the closer the outermost electrons are to the nucleus, resulting in higher ionisation energy. 3. Shielding effect: The more inner electron shells there are, the more they shield the outermost electrons from the attraction of the nucleus, resulting in lower ionisation energy.

Trends on the Periodic Table: 1. Ionisation energy generally decreases down a group. Example: The first ionisation energy of lithium (Li) is lower than that of sodium (Na) because lithium has a larger atomic radius and less nuclear charge. 2. Ionisation energy generally increases across a period. Example: The first ionisation energy of oxygen (O) is higher than that of nitrogen (N) because oxygen has a smaller atomic radius and more nuclear charge.

Assignments: 1. Research and write a short paragraph on the factors influencing ionisation energy. 2. Create a table comparing the first ionisation energies of elements in Group 1 (alkali metals) and Group 17 (halogens). 3. Draw a graph showing the trend in first ionisation energy across Period 3 of the periodic table.