Bond length and Bond Strength
Single bonds are the longest of bonds, while triple bonds are the shortest. Other bonds
and atoms in the molecules will have a small effect on the bond length.
How does bond energy compare with the length of the bonds?
As bond length increases, the energy required to break the bond decreases. That
is, more energy is required to break a triple bond than a double bond, and more to break a
double bond than a single bond.
Use Table 5.3 page 179 to get a better understanding
The amount of energy required to break a bond in one mole of molecules (Avogadro’s #)
is called the bond energy.
Drawing Lewis Structures for Simple Molecules and Ions
Guidelines for drawing Lewis Structures
1. Determine the total number of valence electrons in all of the atoms in the
2. Draw a skeleton structure for the molecule by choosing the atom with the largest
number of unpaired electrons as the central atom.
3. Join the atoms with one pair of bonding electrons.
4. Place lone pairs of electrons around all the atoms except the central atom, so that
each atom has a complete octet.
5. If all valence electrons have been used and the central atom does not have a
complete octet, move lone pair electrons to the central atom forming double or
triple bonds where necessary.
6. If all valence electrons have not been used up, check which atoms do not have a
complete octet and add lone pair electrons where necessary.
Read through and practice Sample Problems page 186-189
Complete question 1 page 189