Metals and Nonmetals: An Evidence-Based Comparison
Big idea: metals and nonmetals are broad families of elements. We classify a sample by combining several observations, not by trusting one appearance.
By the end, you can compare luster, electrical conductivity, malleability and brittleness; describe a safe test; recognize important exceptions; and connect properties to uses.
1. What is being classified?
A chemical element is one kind of atom. A simple substance contains atoms of only one element. Copper, aluminium, sulfur and oxygen are examples of simple substances. In this lesson we compare the typical physical properties of metallic and nonmetallic simple substances at room conditions. We do not classify mixtures such as steel or air as single elements.
Typical metals
- often shiny when freshly cleaned;
- usually conduct electricity and heat well;
- many can be hammered into sheets: they are malleable;
- many can be drawn into wire: they are ductile;
- most are solids at room temperature.
Typical nonmetals
- often lack metallic luster;
- usually conduct electricity poorly;
- solid samples are commonly brittle rather than malleable;
- may be solid, liquid or gas at room temperature;
- show a wider variety of appearances.
These are trends, not absolute rules. Graphite is a nonmetallic form of carbon that conducts electricity. Iodine crystals can look shiny. Mercury is a liquid metal at room temperature. Use several pieces of evidence.