General Chemistry - Molecular Shapes

You may be asked to figure out the shape of certain molecules, so this is how you go about finding them.

Count the number of atoms to which the central atom of the molecule is bound.
1. If the number is 2, then the shape of the molecule is usually:

A) Linear, if the Lewis dot structure shows no unshared pair of atoms on the central atom, but it is,
B) Bent, if the Lewis dot structure does show one or more unshared pairs of electrons on the central atom.

2. If the number is 3, the molecule is:

A) Trigonal planar, if the Lewis dot shows no unshared pair of atoms on the central atom, but it is,
B) Trigonal pyramidal, if the Lewis dot structure does show an unshared pair of electrons on the central atom.

3. If the number is 4, the molecule is usually tetrahedral.

The Mole :
The mole is a unit. One mole of anything is 6.0 × 1023 of that thing. This number is also called Avogadro’s number.

Units of Temperature :
Temperature is measured in either degrees Celsius or degrees Kelvin. Degrees in Kelvin (°K) = degrees in Celsius (°C) + 273. Remember that absolute zero is 0°Kelvin which corresponds to -273°Celsius.