9.1. Lewis Electron Dot Structures http://www.ck12.org
9.1 Lewis Electron Dot Structures
Lesson Objectives
- Define and give examples of covalent bonds.
- Describe the differences between ionic and covalent bonds.
- Describe Lewis structures.
- Use Lewis structures to illustrate covalent bonds in molecules.
Lesson Vocabulary
- covalent bond: Forms when two or more elements share electrons.
- Lewis structure: One way of representing covalent bonds.
- lone pair: An unbonded pair of electrons.
- double bond: A covalent bond in which each atom shares 2 valence electrons.
- triple bond: A covalent bond in which each atom shares 3 valence electrons.
Check Your Understanding
Recalling Prior Knowledge
- What are valence electrons?
- How are electrons configured in s and p orbitals?
- What are electron dot diagrams?
- What is the octet rule?
- What are ions?
Introduction
Ionic substances are completely held together by ionic bonds. The full charges of the ions (for example, Na+and
Cl−in sodium chloride) cause electrostatic interactions that result in a stable crystal lattice. We saw in the previous
chapter that most ionic compounds have high melting points, are brittle, are often soluble in water, and conduct
electricity when melted or dissolved in water. Ionic compounds exist as extended, orderly arrangements of ions. As
we will see, this is quite different from the structure of molecular substances, which take the form of collections
of individual molecules. The atoms within a molecule are held very strongly together, but the interactions between
different molecules are significantly weaker.
Ionic bonds are possible because the elements involved have either donated or accepted one or more electrons.
Sodium chloride is formed when each sodium atom donates its single valence electron to a chlorine atom. As a