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First Ionisation Energy

The First Ionisation Energy is the energy needed to remove one electron from each atom of one mole of atoms in their gaseous state to form one mole of gaseous +1 ions, under standard conditions.The equation representing the first ionisation energy of magnesium is:Mg(g) → Mg+(g) + e-Energy is required to remove electrons, so ionisation energies are endothermic.The Second Ionisation Energy is the energy needed to remove one electron from each ion of one mole of gaseous +1 ions to form one mole of gaseous +2 ions, under standard conditions. For magnesium:Mg+(g) → Mg2+(g) + e-

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Specification: AQA Chemistry (7404), AS-level, 3.1.1.3 Electron configuration. Topic: Atomic Structure.

Key terms in this lesson

Mole
The amount of substance that contains as many particles as there are atoms in exactly 12g of carbon-12.
Endothermic
Describes a reaction in which energy is transferred from the surroundings to the system, so the enthalpy change is positive.
Standard conditions
A pressure of 100 kPa, a temperature of 298 K, and, for solutions, a concentration of 1 moldm-3.

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