BRAINCAKEPolyatomic Ions
The carbonate CO32- and nitrate ions NO3- are trigonal planar as they both have three bonding regions of electron density surrounding the central atom.
The shape of a polyatomic ion is predicted in exactly the same way as for a molecule: count the bonding regions and lone pairs around the central atom, then apply electron pair repulsion theory. The charge on the ion must be included when counting the electrons.
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Key terms in this lesson
- electron pair repulsion theory
- Electron pairs around a central atom arrange themselves as far apart as possible to minimise repulsion, deciding molecular shape.
- lone pair
- A pair of outer shell electrons on an atom that is not involved in bonding.
- oxonium ion
- The ion H3O+, formed when a water molecule accepts a proton from an acid.
More in Discrete Molecules
- The Shapes of Molecules
- Molecules with Multiple Bonds
- Bond Angles
- Shape and Polarity
- London Forces
- Permanent Dipoles
- Hydrogen Bonds
- Intermolecular Forces and Boiling Points
All 25 lessons in Discrete Molecules · All Edexcel AS-level Chemistry topics