Doc Brown's Advanced A Level Chemistry

Theoretical Physical Chemistry Revision Notes

The shapes of Molecules and Ions and bond angles related to their Electronic Structure

Part 2 Some other molecules and ions of carbon, nitrogen, sulphur and chlorine

A description, explanation, shapes and bond angles of the carbonate ion, nitrate(III) ion (nitrite ion), nitrate(V) ion (nitrate ion), nitrogen(IV) oxide (nitrogen dioxide), nitronium ion, sulfur(IV) oxide (sulphur dioxide), sulfur(VI) oxide (sulphur dioxide), sulfate(IV) ion (sulphate ion), sulfur(VI) ion (sulphate ion), chlorate(III) ion, ClO₂^- (chlorite ion), chlorate(V) ion, ClO₃^- (chlorate ion) and the chlorate(VII) ion, ClO₄^- (perchlorate ion) are all described and discussed.

SHAPES OF MOLECULES INDEX: two other pages

Introduction - theory - lots of inorganic molecule/ion examples

shapes and bond angles of organic molecules

Molecule shapes, dot and cross diagrams, bond angles for selected molecules and ions of nitrogen, sulfur and chlorine using the valence-shell electron-pair repulsion model (VSEPR) and the dot and cross (ox) diagrams are presented in 'Lewis style' The 'scribbles' will be replaced by neat diagrams eventually!

Carbon in Group 4/14

• Carbonate ion, CO₃^2- is trigonal planar in shape with a O-C-O bond angle of 120^o because of three groups of bonding electrons and no lone pairs of electrons.
• The shape is deduced below using dot and cross diagrams and VSEPR theory and illustrated below.
• Note that all the C-O bonds are identical due to delocalisation of some of the electrons (σ sigma and π pi bonding)

valence bond dot and cross diagram for the carbonate ion

2. Nitrogen in Group 5/15

• Nitrogen(IV) oxide, NO₂ (nitrogen dioxide) is bent shaped (angular), O-N-O bond angle ~120^o because of two bonding groups of bonding electrons and a single lone electron in the same plane as the bonding pairs of electrons.
• The nitrate(III) ion, NO₂^- (nitrite ion) is bent shaped (angular), O-N-O bond angle ~120^o due to two groups of bonding electrons and one lone pair of electrons.
• The nitrate(V) ion, NO₃^- (nitrate ion) is trigonal planar, O-N-O bond angle 120^o due to three bonding groups of electrons and no lone pairs of electrons.
• The nitronium ion, NO₂⁺, is linear, O-N-O bond angle of 180^o because there are two groups of bonding electrons and no lone pairs of electrons (you easily see this from the NO₂ neutral molecule diagram below).
• The shapes are deduced below using dot and cross diagrams and VSEPR theory and illustrated below.

valence bond dot and cross diagrams for nitrogen oxides and nitrogen oxyanions

• Note that all the N-O bonds within the molecule or ion are identical due to delocalisation of some of the electrons (σ sigma and π pi bonding)

Sulfur in Group 6/16

• Sulfur(IV) oxide, SO₂ (sulphur dioxide/sulfur dioxide) molecule is a bent shape (angular), O-S-O bond angle ~120^o due to two groups of bonding electrons and one non-bonding lone pair of electrons.
• The sulfate(IV) ion/sulphate(IV) ion, SO₃^2- (sulfite ion/sulphite ion) is a trigonal pyramid shape, O-S-O bond angle ~109^o due to three groups of bonding electrons and one lone pair of electrons.
• Sulphur(VI) oxide/sulfur(VI) oxide, SO₃ (sulfur trioxide/sulphur trioxide), is a trigonal planar shape, O-S-O bond angle of 120^o due to three bonding groups of electrons and no lone pairs of electrons.
• Sulfate(VI) ion/sulfate(VI) ion, SO₄^2- (sulphate ion/sulfate ion) is tetrahedral in shape, O-S-O angle of 109.5^o. due to four groups of bonding electrons and no lone pairs of electrons.
• The shapes are deduced below using dot and cross diagrams and VSEPR theory and illustrated below.

 valence bond dot and cross diagrams for sulfur oxides and sulfur oxyanions

• Note that all the S-O bonds within the molecule or ion are identical due to delocalisation of some of the electrons (σ sigma and π pi bonding)

Chlorine in Group 7/17

• The chlorate(III) ion, ClO₂^- (chlorite ion), is bent shaped (angular), O-Cl-O bond angle ~109^o because of two groups of bonding electrons and two lone pairs of electrons.
• The chlorate(V) ion, ClO₃^- (chlorate ion), is a trigonal pyramid shape, O-Cl-O bond angle ~109^o because of three groups of bonding electrons and one lone pair of electrons.
• The chlorate(VII) ion, ClO₄^- (perchlorate ion), is a tetrahedral shape, O-Cl-O bond angle 109.5^o due to four groups of bonding electrons and no lone pairs of electrons.
• The shapes are deduced below using dot and cross diagrams and VSEPR theory and illustrated below.

valence bond dot and cross diagrams for selected chlorate ions

• Note that all the Cl-O bonds within the molecule or ion are identical due to delocalisation of some of the electrons (σ sigma and π pi bonding)

Revision notes for GCE Advanced Subsidiary Level AS Advanced Level A2 IB Revise AQA GCE Chemistry OCR GCE Chemistry Edexcel GCE Chemistry Salters Chemistry CIE Chemistry, WJEC GCE AS A2 Chemistry, CCEA/CEA GCE AS A2 Chemistry revising courses for pre-university students (equal to US grade 11 and grade 12 and AP Honours/honors level courses)

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