Lewis Structures
- Lewis structures are simplified electron shell diagrams and show pairs of electrons around atoms.
- A pair of electrons can be represented by dots, crosses, a combination of dots and crosses or by a line. For example, chlorine can be shown as:
Different Lewis Structures for chlorine molecules
- Note: Cl–Cl is not a Lewis structure, since it does not show all the electron pairs.
- The “octet rule” refers to the tendency of atoms to gain a valence shell with a total of 8 electrons
Steps for drawing Lewis Structures
- Count the total number of valence
- Draw the skeletal structure to show how many atoms are linked to each other.
- Use a pair of crosses or dot/cross to put an electron pair in each bond between the atoms.
- Add more electron pairs to complete the octets around the atoms ( except H which has 2 electrons)
- If there are not enough electrons to complete the octets, form double/triple bonds.
- Check the total number of electrons in the finished structure is equal to the total number of valence electrons
Worked example
Draw a Lewis structure for CCl4
Answer:
Steps in drawing the Lewis Structure for CCl4
Further examples of Lewis structures
- Follow the steps for drawing Lewis structures for these common molecules