Understanding Linear Geometry
Linear geometry means that all three atoms lie in a straight line with a bond angle of 180°.
Examples:
* Carbon dioxide (CO2): The carbon atom is in the center, with two oxygen atoms on either side. The molecule is linear because the carbon atom has two double bonds with the oxygen atoms, and the electron pairs repel each other as far apart as possible, resulting in a straight line.
* Hydrogen cyanide (HCN): The carbon atom is in the center, with one hydrogen atom and one nitrogen atom on either side. The molecule is linear because the carbon atom has a triple bond with the nitrogen atom and a single bond with the hydrogen atom. Again, electron repulsion forces a linear arrangement.
Conditions for Linearity
* Central atom must have two electron domains: These electron domains can be single bonds, double bonds, or triple bonds.
* No lone pairs on the central atom: Lone pairs of electrons would cause repulsion and distort the linear geometry.
Key Takeaway:
A molecule with three atoms can be linear if the central atom has two electron domains and no lone pairs.
