Hard Acid
| Formula / Notation | Hard acid: small, highly charged, low polarisability (e.g., H⁺, Mg²⁺, Al³⁺) |
|---|---|
| Also Known As | Hard Lewis acid, HSAB hard acid, class (a) acid (older term) |
What is Hard Acid?
In HSAB (Hard Soft Acid Base) theory, a Lewis acid that is small, has high positive charge, and is not easily polarized. Hard acids form stronger bonds with hard bases. Examples include H⁺, Mg²⁺, Al³⁺, and BF₃. They prefer interactions with oxygen-donor ligands.
Formula & Notation
Other Names / Synonyms: Hard Lewis acid, HSAB hard acid, class (a) acid (older term)
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
In HSAB (Hard Soft Acid Base) theory, a Lewis acid that is small, has high positive charge, and is not easily polarized. Hard acids form stronger bonds with hard bases. Examples include H⁺, Mg²⁺, Al³⁺, and BF₃. They prefer interactions with oxygen-donor ligands.
HSAB theory predicts stability of coordination compounds (hard acids bind hard bases; soft acids bind soft bases), explains solubility trends (CaF₂ is insoluble — hard-hard; CaI₂ is soluble), guides catalyst design, and rationalises biological metal ion selectivity in metalloproteins.
No direct safety concern for the concept. Hard Lewis acids in high concentration (Al³⁺, Fe³⁺ in acidic solutions) can cause skin and eye irritation. BF₃ (hard Lewis acid) is a toxic gas that reacts with moisture. HSAB principles help predict which ligands will effectively chelate toxic metal ions (e…
The formula or notation for Hard Acid is: Hard acid: small, highly charged, low polarisability (e.g., H⁺, Mg²⁺, Al³⁺)