MOLECULAR GEOMETRY TYPES

MOLECULAR GEOMETRY
ORGANIC MOLEC. GEOMETRY  Elmhurst College
Lewis Diagrams Trigonal Planar  Trigonal Pyrimid  Chemistry Department
Linear Tetrahedral Bent  Virtual ChemBook

 Linear Molecular Geometry

Beryllium Hydride:

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An example of linear electron pair and molecular geometry is BeH2. This molecule is electron deficient and does not follow the octet rule because it has only 4 valence electrons. The hydrogen atoms are as far apart as possible if opposite each other at 180o. This is linear geometry.

Beryllium hydride is a solid at room temperature. It does not have any common uses. All beryllium compounds are quite toxic.

   

 Carbon Dioxide:

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In this example, CO2, the Lewis diagram shows carbon at the center with no lone electron pairs. The carbon and and both oxygen are bonded through double bonds which counts as "two electron pairs". Hence the molecule has two electron pairs and is linear.

Carbon dioxide is the major product of all combustion reactions involving carbon based materials such as natural gas, gasoline, and coal. Carbon dioxide is the end product of animal/human metabolism/respiration. It is also the gas that provides the carbonation in soda and beer.

Carbon dioxide is the major gas implicated in the greenhouse effect or global warming. The gas in the atmosphere acts to trap heat that might otherwise escape from the earth to outer space.

   

 Hydrogen Cyanide:

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In this example, HCN, the Lewis diagram shows carbon at the center with no lone electron pairs. The carbon and nitrogen are bonded through a triple bond which counts as "one electron pair". Hence the molecule has two electron pairs and is linear.

Hydrogen cyanide is prepared on an industrial scale by the reaction of methane with ammonia in the presence of a platinum catalyst at 1200oC. It boils at 25oC, and thus is a gas a room temperature. HCN is very toxic and will cause death in a matter of minutes if inhaled or ingested.