Geometry

1. Atoms, bonds and lone pair of electrons on a central atom repel each other.
2. An atom bonded to four different groups, including lone pairs of electrons, is said to be tetrahedral because the four groups form a tetrahedral arrangement around the center atom, not square planar like cis and trans platinum.  LeBel proved this.
3. The angle between two bonds to a tetrahedral atom is approximately 109.5°.  Can you prove this?
4. Ignoring unsaturations, an atom bonded to three different groups, including lone pairs of electrons, is said to be trigonal because the three different groups form a triangle arrangement around the center atom. 
5. The angle between two bonds to a trigonal atom is approximately 120°.
6. Ignoring unsaturations, an atom bonded to two different groups, including lone pairs of electrons, is said to be linear because the two different groups form a line with the center atom. 
7. The angle between two bonds to a linear atom is 180°.

Exam question 7:  How many tetrahedral, trigonal or linear atoms are in a given structure?

Hybridization

1. Tetrahedral atoms are called sp³ hybridized or have sp³ hybridized atomic orbitals that overlap with other orbitals with s character to make sigma bonds.
2. 3 p's require three dimensions.
3. Trigonal atoms are called sp² hybridized or have sp² hybridized atomic orbitals that overlap with other orbitals with s character to make sigma bonds.  The left over p orbital is used to make a pi bond.
4. 2 p's require two dimensions.
5. Linear atoms are called sp hybridized or have sp hybridized atomic orbitals that overlap with other orbitals with s character to make sigma bonds.  The left over p orbitals are used to make two pi bonds.
6. 1 p requires one dimension.
7. Unpaired electrons have no clout.
8. Hydrogens only have s atomic orbitals to overlap.

Exam question  8:  How many s, sp, sp² or sp³ hybridized atoms does a given structure have?

Bond Lengths

1. Carbon hydrogen bonds have a length of 1.1 angstroms, Å.
2. Carbon-carbon triple bonds have a length of 1.2 Å.
3. Carbon-carbon double bonds have a length of 1.3 Å.
4. Carbon-carbon 1.x bonds have a length of 1.4 Å.
5. Carbon-carbon single bonds have a length of 1.5 Å.
6. The more electronegative the atoms bonding, the shorter the bond length.
7. Our online program is deficient in calculating bond lengths.

Exam question  9:  How many carbon-carbon bonds are 1.2, 1.3, 1.4 or 1.5 Å long.