2. Chemical Bonding
1. How do we calculate formal charge?
1. Break the bonds in the molecule.
2. Split the electrons equally between the atoms
in each bond
3. FC = no. e gain/lost
4. Chemical Bonding
1. How do we calculate formal charge?
Formal charges are incurred when:
1. there are dative bonds
2. atom gains/ loses electrons
5. Chemical Bonding
2. How do we calculate bond order?
1. Bond order represents the number of covalent
bonds between 2 atoms.
It is usually an integer unless delocalisation of
pi bonds are possible.
6. Chemical Bonding
2. How do we calculate bond order?
Example: SO42–
Due to delocalisation of pi bonds in the ion, there are 1.5
bonds between each S and O atom.
7. Chemical Bonding
3. How does bond order relate to bond length?
• Bond order represents the number of covalent bonds
between 2 atoms.
• The greater the no. of bonds between 2 atoms, the
stronger the bond, the shorter the bond length.
8. Chemical Bonding
4. Is a lone electron considered an electron
domain i.e. lone pair?
• Yes. The lone electron is consider as a lone pair
when assigning shape.
• Example: NO2 [2 bp, 1 lp] V shaped
9. Chemical Bonding
5. When do we use double bond or dative bond?
• In drawing Lewis structures, double bonds are
preferred since they do not incur formal charge.
• Dative bonds are used when the central atom cannot
expand beyond octet.
10. Chemical Bonding
6. How do we determine if a molecule is polar?
1. Look at the bonds in the molecule; are the polar (i.e.
do the atoms have different electronegativities?)
Example:
C–H bond non polar
C–Cl bond polar
11. Chemical Bonding
6. How do we determine if a molecule is polar?
2. If the molecule consists of polar bonds, determine if
the dipoles cancel out.
Example:
