Shapes with Three Electron Groups Trigonal Planar Arrangement

Molecular Shapes with Three Electron Groups (Trigonal Planar Arrangement) 

When the three electron groups are bonding groups, the molecular shape is trigonal planar (AX3). Boron trifluoride (BF3), another electron-deficient molecule, is an example. It has six electrons around the central B atom in three single bonds to F atoms. The nuclei lie in a plane, and each F—B—F angle is 120°  

The nitrate ion (NO3 ) is one of several polyatomic ions with the trigonal planar shape. One of three resonance forms of the nitrate ion (Sample Problem 10.4) is 

The resonance hybrid has three identical bonds of bond order I5, so the ideal bond angle is observed. 

Effect of Double Bonds How do bond angles deviate from the ideal angles when the suiTOunding atoms and electron groups are not identical Consider formaldehyde (CH2O), a substance with many uses, including the manufacture of Formica countertops, the production of methanol, and the preservation of cadavers. Its 

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