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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.
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. For magnesium:Mg+(g) → Mg2+(g) + e-

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Specification: OCR Chemistry A (H032), AS-level, 2.1.1 Atomic structure and isotopes. Topic: Atoms, Ions and Compounds.

Key terms in this lesson

Ion
A positively or negatively charged atom or group of atoms, formed by the loss or gain of electrons.
Ionisation
The loss or gain of electrons by an atom or molecule to form a charged ion.
Mole
The amount of substance that contains as many particles as there are atoms in exactly 12g of carbon-12.
Endothermic
Describes a process in which heat 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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