First Ionisation Energy
| Formula / Notation | IE₁: M(g) → M⁺(g) + e⁻; increases across period, decreases down group |
|---|---|
| Also Known As | First ionisation potential, IE₁, first IP, IE1 |
What is First Ionisation Energy?
The energy required to remove the outermost electron from a neutral gaseous atom, forming a +1 ion. Ionization energies generally increase across a period and decrease down a group. Discontinuities in ionization energy trends provide evidence for electron shell structure.
Formula & Notation
Other Names / Synonyms: First ionisation potential, IE₁, first IP, IE1
Properties & Characteristics
Uses & Applications
Safety Information
Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.
Key Facts
Frequently Asked Questions
The energy required to remove the outermost electron from a neutral gaseous atom, forming a +1 ion. Ionization energies generally increase across a period and decrease down a group. Discontinuities in ionization energy trends provide evidence for electron shell structure.
IE₁ values predict metal reactivity, explain periodic trends in metallic/non-metallic character, guide prediction of accessible oxidation states, and are key data in Born-Haber cycle calculations. Anomalies in IE₁ trends (e.g., O < N in Period 2) are explained by electron pair repulsion in p orbital…
Elements with very low IE₁ (alkali metals: Na, K, Li) react violently with water and air. Their extreme reactivity is a consequence of easily removing their single valence electron. Store under mineral oil or inert gas; never expose to water.
The formula or notation for First Ionisation Energy is: IE₁: M(g) → M⁺(g) + e⁻; increases across period, decreases down group