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Ionisation Energy

IE_n: X^(n-1)+ (g) → X^n+(g) + e⁻; successive IEs always increase
Quick Reference
Formula / NotationIE_n: X^(n-1)+ (g) → X^n+(g) + e⁻; successive IEs always increase
Also Known AsIonisation potential, IE, electron removal energy, IP

What is Ionisation Energy?

The energy required to remove an electron from a gaseous atom or ion to form a positive ion. First ionisation energy is the energy to remove the outermost electron from a neutral atom. Successive ionisation energies show large jumps when inner shell electrons are removed.

Formula & Notation

IE_n: X^(n-1)+ (g) → X^n+(g) + e⁻; successive IEs always increase

Other Names / Synonyms: Ionisation potential, IE, electron removal energy, IP

Properties & Characteristics

Ionisation energy (IE) is the energy required to remove an electron from a gaseous atom or ion to form a positively charged ion. The first ionisation energy (IE₁) removes the most loosely held electron. Successive ionisation energies (IE₂, IE₃, ...) are always greater (more energy needed to remove from increasingly positive ion). Dramatic jumps in IE occur when an inner-shell (core) electron is removed. IE increases across a period and decreases down a group.

Uses & Applications

Ionisation energies are used in: Born-Haber cycle calculations (lattice energy determination), predicting oxidation states accessible to elements, understanding periodic trends in reactivity and metallic character, designing photoionisation detectors in chromatography, and calibrating photoelectron spectroscopy (PES).

Safety Information

No direct safety concern for the concept. Elements with low IE₁ (alkali and alkaline earth metals) are dangerously reactive toward air and water because the valence electron is so easily removed. Knowledge of IE guides prediction of which metals react violently under normal conditions.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Ionisation Energy
Formula IE_n: X^(n-1)+ (g) → X^n+(g) + e⁻; successive IEs always increase
Synonyms Ionisation potential, IE, electron removal energy, IP

Frequently Asked Questions

The energy required to remove an electron from a gaseous atom or ion to form a positive ion. First ionisation energy is the energy to remove the outermost electron from a neutral atom. Successive ionisation energies show large jumps when inner shell electrons are removed.

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