Molecular Geometry

Molecular Geometry surrounds the molecule's orientation in space. Believe it or not, a molecule is not just a jumbled mass of atoms, spinning wherever they want to. Molecules are strictly ordered in certain arrangements depending upon the number of constituent atoms, unpaired electrons, etc.

Here is an example of two molecules' arrangements:

There is one important theme running throughout these examples:

The molecules are composed of more than 2 atoms.
What is so special about a molecule with only 2 atoms?
When a molecule is composed of only two atoms, it prefers to lie in a straight line, or in a linear fashion. Geometry has taught us that two points define a straight line, and that same principle is true for chemistry. The two atoms will define the straight line, therefore causing the linear arrangement.
What happens when there are more than two atoms in a molecule?
This is where the fun begins! The atoms will tend to avoid each other due to their associated electrons in their orbitals and the charge they represent. The atoms (and their respective electrons) are not unlike people in a sense that they tend to avoid each other to a certain degree. People have a circle around themselves known as a personal space. You can easily demonstrate this by walking up to a friend and start talking to them. As you are in a discussion, start to move closer. Unconsciously, they will begin to move away as you invade their personal space. Atoms are the exact same way! They have their own "personal space", and their definition of this space will form the framework for their molecular geometry. Chemists have a fancy name for this theory called: the VESPER Theory
Is there a name for the distance between atoms in a molecule?
Does chemistry have a name for everything? Of course! The name for the distance between atoms in a molecule is called the bond angle. The distance is measured in angles because in essence, the molecule makes a circle with its atoms.
What are the names for the fancy shapes?
  • Linear: The electrons are repelling to produce the absolute most distance between each other, therefore producing 180 degree bond angles.
  • Trigonal Planar: The atoms are directed towards the corners of an equilateral triangle, therefore producing bond angles of 120 degrees.
  • Tetrahedron: The atoms are in the corners of a tetrahedron.
  • There are many more identified shapes for molecular geometry. This is just an introduction!

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