Lesson 1: 2.1 Types of Chemical Bonds

How does the difference in electronegativity between two bonding atoms determine whether electrons are shared equally, shared unequally, or transferred?
How can we use physical properties like melting point and electrical conductivity to classify an unknown substance as ionic, covalent network, molecular covalent, or metallic?

Electronegativity
Ionic Bond
Polar Covalent Bond
Nonpolar Covalent Bond
Metallic Bond
Conductivity
Crystal Lattice

Learning Objective 2.1.A; Suggested Skill 6.A (Argumentation - Make a scientific claim)

Students categorize bonds along a continuous spectrum of electron density distribution. They must understand that high differences in electronegativity result in ionic character, intermediate differences yield polar covalent character, and negligible differences create nonpolar covalent bonds. They will map these particulate traits directly to macroscopic behaviors (e.g., phase at room temperature, hardness, and conductivity).

Support: Provide a color-coded number line matrix mapping electronegativity differences to specific bonding zones (0–0.4 = Nonpolar Covalent; 0.5–1.7 = Polar Covalent; >1.7 = Ionic).
Extension: Provide students with a data set for an ambiguous material (like gallium arsenide, GaAs) and have them argue whether it behaves more closely to a covalent network or an ionic solid.

Sample Problem: A solid, crystalline compound is found to have a high melting point (801 degrees C). It is a non-conductor of electricity in its solid state but becomes highly conductive when dissolved in water or melted into a liquid.

1. Classify the type of bonding present in this substance.

2. Explain the structural reason why the compound can conduct electricity as a liquid but not as a solid.