Trigonal Pyramidal: 3 bonding pairs, 1 lone pair.

This is an example of a Trigonal pyramidal molecule. It has angles all of which are 107°, and is a 3-dimensional structure. This example is of ammonia. Nitrogen, the central atom, has 5 valence electrons, 3 of which are bonded to hydrogen’s electrons. However, 2 of nitrogen’s valence electrons are not being used for bonding and create a lone pair. Examples: NH3, PCl3.

Trigonal Bipyramidal: 5 Bonding Locations and No Lone Pairs

This is an example of a Trigonal bipyramidal molecule. It has 120°, 180°, and 90° angles and is a 3-dimensional structure. This particular molecule is Phosphorus pentachloride. The lewis dot structure is composed of 40 valence electrons 5 bonding locations and 0 lone pairs on the central atom. Examples: PF5, SF4.

See Saw : Four Bonding Locations and One Lone Pairs

This is an example of the seesaw molecule that contains one lone pair. The lone pair is located on the right side of the molecule, forcing the other atoms to create a 90 degree angle between them in a 2-dimensional structure. This particular molecule is SULFURIC FLORIDE, SF4.

Octahedral: No Lone Pairs, 6 Bonding Locations

This is an example of a octahedral molecule that contains no lone pairs. This is a Sulfur hexaflouride molecule, SF6, which contains 48 valence electrons to use for the lewis dot structure. When the lewis dot structure is drawn there are six bonding locations and no lone pairs on the central atom. This type of configuration would give you a octahedral geometry. The angles are 90 degrees all around except for opposite atoms, which would be 180 degrees. Other octahedral molecules would be SCl6, SeF6, and SeBr6. Click on the top picture to see the rotation of the molecule.

Square Pyramydal Geometry: 1 lone pair and 5 bonding groups

This BrF5, Bromine pentaflouride, molecule is an example of a square pyramidal geometry. The square pyramydal shape has one lone pair and five bonding groups. The angles are 90 degrees between all the molecules and the top molecule. The angles between all the molecules on the side are 90 degrees also. But between opposite molecules the angle is 180 degrees. The Lewis dot structure for BrF5 has 30 valence electrons and when drawn you have five bonding locations and one lone pair.

T-Shaped: 3 Shared Pairs and 2 Lone Pairs

This is an example of a t-shaped molecule. A t-shaped molecule has three shared pairs and two lone pairs. The bond angles are either 90 degrees or 180 degrees, but in the case of bromine trifluoride, the bond angle is 86.2 degrees. Bromine trifluoride has 28 valence electrons, and when you do the Lewis dot structure you are left with two lone pairs and three shared pairs around the central atom. Other examples of t-shaped molecules are ClF3 and IF3.

Tetrahedral: 0 lone pairs, 4 bonding locations

This is an example of a tetrahedral molecule that contains no lone pairs. This is a silicon chloride molecule, SiCl4, which has 32 valence electrons to use for the lewis dot structure. When the lewis dot structure is drawn there are four bonding locations and no lone pairs on the central atom. This type of configuration would give you a tetrahedral geometry. This geometry an angle between the atoms which is 109.5° degrees all around. Quiz Yourself: CH4,CCl4, SiF4, SnCl4

Trigonal Planar: Three Bonding Locations, Zero Lone Pairs

This is an example of a trigonal planar molecule that contains no lone pairs. This is a boron fluoride molecule, BF3, which has 24 valence electrons to use for the lewis dot structure. When the lewis dot structure is drawn there are three bonding locations and no lone pairs on the central atom. This type of configuration would give you a trigonal planar geometry. This geometry has only one angle between the atoms which is 120 degrees. Try it with these other linear molecules: Aluminum chloride (AlCl3) and Boron chloride (BCl3).

Bent: 1 lone pair, 2 bonding locations

This is an example of a Bent molecule that contains 1 lone pair. The lone pair is located at the top of the molecule, forcing the other atoms to move down and create a 118° angle between them in a 2-dimensional structure. There must also be a double bond in order to complete the octect rule for the central atom. This particular molecule isSelenium Oxide, SeO2. The lewis dot structure is composed of 18 valence electrons, 2 bonding locations, and 1 lone pair on the central atom.

Examples to test your skills: SO2, SeS2, SeO2

Square Planar Molecule : 4 bonding locations and 2 lone pairs

This is an example of a square planar molecule that contains 2 lone pairs. The lone pairs are located at the bottom and top of the molecule, forcing the other atoms to create 90° angles between them and line up in a 2-dimensional structure. This particular molecule is iodine chloride, ICl4. The lewis dot structure is composed of 36 valence electrons, 4 bonding locations, and 2 lone pairs on the central atom. Some other examples you can try are XeF4 and SF4.

Website, Angles and Lone Pairs

http://www.chem.ufl.edu/~chm2040/Notes/Chapter_11/shapes.html

This is a good website to see the different structures for the various molecular geometries. Remember you must know the actual angle for each and not just < 109.5. And the website can be used to see how the lone pairs should be shown. You must create your own picture using Paint or any other program.

http://misterguch.brinkster.net/VSEPR.html

This is a good website to get the angles for the molecular geometries.

Linear Molecule : Two bonding locations and No Lone Pairs

This is an example of a linear molecule that contains no lone pairs. This is the carbon dioxide molecule, CO2, which has 16 valence electrons to use for the lewis dot structure. When the lewis dot structure is drawn there are two bonding locations and no lone pairs on the central atom. This type of configuration would give you a linear molecular geometry. This geometry has only one angle between the atoms which is 180 degrees. Try it with these two other linear molecules: Hydrogen cyanide (HCN) and ethyne (C2H2).

Welcome

Hello and Welcome to the WHS AP CHEM blog website. This will be used for discussion of problems or projects. It will be used to post what is going on in class and what is coming up.