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Lewis Structure Worksheet
Lewis Theory Notes
1. Valence electrons play a fundamental role in chemical bonding.
2. Sometimes bonding involves the TRANSFER of one or more electrons from one atom to another.
This leads to ion formation = IONIC BONDS.
3. Sometimes bonding involves SHARING electrons between atoms = COVALENT BONDS.
4. Electrons are transferred or shared such that each atom gains a more stable electron configuration.
- Usually changes to NOBLE GAS configuration (i.e. having 8 electrons in its outer shell)
- This arrangement (having 8 electrons on the outer shell) is called an OCTET.
Lewis Structures & Electron Dot Diagrams
- Show the valence electrons of an atom/ion
- Chemical symbol represents the nucleus and the inner electrons
- Dots represent the valence electrons
* Since elements in the same family have the same number of valence electrons, their dot diagrams will look similar
*Lewis dot diagrams only work well for representative elements
- Transition metals, lanthanides, and actinides have incompletely filled inner shells (d or f orbitals), so we
can’t make simple Lewis Diagrams for them
Drawing Lewis Structures for IONIC COMPOUNDS
- Draw the Lewis Dot Diagram for each of the ions involved à including the ion charge
Drawing Lewis Structures for COVALENT COMPOUNDS
1. Count the total number of valence electrons for the molecule
2. Determine which atoms are bonded together and put two electrons between them to represent the bond
3. Place remaining valence electrons to complete the octets of the atoms around the central atom. If any remain,
place them in pairs on the central atom.
4. If the central atom has less than 8 electrons, have a neighbouring atom share electrons with the deficient atom
by putting an extra pair of electrons into a shared bond (repeat if needed).
5. Replace the bonding pair(s) of electrons with dashes to represent the bonds.
- Bonding Pairs: the electrons that are transferred/shared in a bond
- Lone Pairs: electrons not involved in bonding
Multiple Bond Examples
1. a) When the distance between two covalently-bonded atoms increases, what happens to the electrostatic
attraction of their nuclei to the shared electrons in a covalent bond?
b) What would you expect to happen to the strength of a covalent bond between tow identical halogen atoms when
going down the halogen family from F2 to I2?
2. What would you expect to happen to the strength of a covalent bond when the number of shared electrons
increases?
3. The distance between the nuclei of two atoms involved in a bond is called the BOND LENGTH. What should
happen to the bond length as the number of shared electrons in the bond increases?
Why will this happen?
PRACTICE: Identify the type of compound and depict the bonding with Lewis Structures (electron dot diagrams) for
each of the following:
a) CaS
d) MgBr2
g) CCl4
b) N2
e) LiBr
h) SI2
c) PH3
f) SiO2