4.2 Geometry

4.2 Geometry

• You will be able to easily determine the geometry of an atom if you can determine its hybridization state.
• Let's do another example.

• The nitrogen atom is in ammonia.

• How many atoms are connected to this nitrogen atom?
• There are three hydrogen atoms.
• We need to know how many lone pairs the nitrogen atom has.
• It has one pair.

• We take the sum.

• The central car Bon atom is the hybridization state for each compound.

• The following molecule has a carbon atom.
• The hydrogen atoms are not shown.

• If you look at the number of bonds, you don't need to count anymore.

• We need to know the geometry of each of the three hybridization states now that we know how to determine them.
• The electrons in the outermost shell want to be as far apart from each other as possible.

• We can predict the geometry around most atoms with this simple idea.
• There are three types of hybridized orbitals.

• Think of this as a tripod with a leg sticking up in the air.

• Students get confused here.
• The molecule's geometry is affected by the geometry of the orbitals.

• An example can be looked at.

• Only three of the orbitals are responsible for bonds.
• If we only look at the atoms that are connected, we don't see a triangle.

• There are three bonds pointing away from the central nitrogen atom and it's shaped like a pyramid.

• Two of these orbitals are being used for bonds, while the other two are occupied by lone pairs.
• We don't see a tetrahedron if we focus only on the atoms that are connected.

• There are six different types of geometry.
• The hybridization state is determined first.
• We can figure out which of the six different types of geometry we are dealing with using the number of lone pairs.
• Let's see if it works on a problem.

• The first thing we need to do is figure out the hybridization state.

• Next, we remind ourselves of how many lone pairs there are.
• The geometry has to be trigonal.

• If you can determine the geometry around an atom, you should be able to determine the shape of a molecule.
• You can repeat your analysis for each atom.
• This may seem like a large task at first, but once you get the hang of it, you will be able to determine the geometry of an atom.

• You should be able to do these problems very quickly if you get to the point where you can.
• The first few will take longer than the last few.
• You will need more practice if the last problem is taking you a long time.
• In the second half of your textbook, open any page if this is the case.
• You are likely to see drawings of structures.

• To determine the geometry of a structure, point to any atom.
• The list above can be used to help you.
• If you can do it without the list, go from one drawing to the next.
• It's important that it's done without the list.

• The following compounds have the same geometry.
• Do not worry about the geometry of the atoms.