Ionisation Energies of Group 2 Elements

Ionisation energy is a crucial concept in understanding the chemical properties of Group 2 elements.

Definition: Ionisation energy is the amount of energy required to remove one mole of electrons from one mole of gaseous atoms of an element to form one mole of gaseous ions.

There are two important types of ionisation energies to consider for Group 2 elements:

1. First ionisation energy: The energy needed to remove the first outer electron of an atom.
2. Second ionisation energy: The energy required to remove the second outer electron from a singly charged ion.

Example: Ionic equation for the formation of a Magnesium ion: Mg(g) → Mg²⁺(g) + 2e⁻

The ionisation energies of Group 2 elements follow a trend:

• They decrease as you move down the group
• The second ionisation energy is always higher than the first

This trend is due to the increasing atomic size and the greater distance between the nucleus and the outermost electrons as you move down the group. The larger atomic size results in weaker attraction between the nucleus and the outermost electrons, making it easier to remove them.

Highlight: The high ionisation energies of Group 2 elements contribute to their strong reducing properties and their tendency to form +2 ions in chemical reactions.

Understanding these ionisation energy trends is crucial for predicting and explaining the chemical properties of Group 2 elements and their compounds.