C. Chemistry: The Nature of Matter · Atoms, Elements and Compounds

Metals, Nonmetals and Metalloids

C2.5 C2.6 A1.2 A1.5About 75 minutes

Learning goals

I can describe the physical and chemical properties of metals, nonmetals and metalloids.
I can investigate the properties of samples and use my results to classify them.
I can locate metals, nonmetals and metalloids on the periodic table using the staircase line.
I can connect these properties to uses of elements in everyday life and in technology.

Words to know

metal
An element that is usually shiny, malleable, ductile and a good conductor of heat and electricity. Metals are on the left of the staircase line.

nonmetal
An element that is usually dull, brittle (if solid) and a poor conductor. Nonmetals are on the right of the staircase line, plus hydrogen.

metalloid
An element with some properties of metals and some of nonmetals, found along the staircase line.

lustre
How shiny a surface is.

malleable
Able to be hammered or rolled into thin sheets without breaking.

ductile
Able to be stretched into a thin wire.

semiconductor
A material that conducts electricity better than an insulator but not as well as a metal; silicon is the best-known example.

Three kinds of elements

Walk through a hardware store and you will find copper pipes, aluminium ladders and steel nails (steel is mostly iron). In the electronics store, nearly every device runs on chips made from silicon. At the pool, chlorine compounds keep the water clean. These elements are useful in very different ways because they belong to three different classes: metals, nonmetals and metalloids.

Property	Metals	Nonmetals	Metalloids
State at room temperature	Solid (except mercury, a liquid)	Many are gases; some solids; bromine is a liquid	Solid
Lustre	Shiny	Dull (solids)	May be shiny
Malleable / ductile?	Yes	No: solids are brittle	No: brittle
Conducts heat and electricity?	Yes, well	Poorly (insulators); graphite, a form of carbon, is an exception	Somewhat: semiconductors
Typical chemical property	Many react with acids, giving hydrogen gas; many corrode	Many react with metals to form compounds	Varies
Electrons in reactions	Tend to lose valence electrons	Tend to gain or share electrons	Can share electrons
Examples	Iron, copper, aluminium, gold, sodium	Oxygen, nitrogen, sulfur, chlorine, carbon	Boron, silicon, germanium, arsenic

Properties of the three classes of elements. Most of the known elements are metals.

Where they are on the periodic table

A zig-zag staircase line runs from boron down to the lower right of the table.

Metals are to the left of the line. They are the large majority of elements.
Nonmetals are to the right of the line, plus hydrogen, which sits in group 1 but is a nonmetal gas.
Metalloids sit along the line: boron, silicon, germanium, arsenic, antimony and tellurium. (Different sources sometimes include one or two more.)

This connects to atomic structure: metals usually have few valence electrons (1, 2 or 3) that they lose easily, while nonmetals usually have many (5, 6 or 7) and tend to gain or share electrons.

The first five periods of the periodic table. Metals (left) and nonmetals (right) are separated by the staircase line; the metalloids sit along it. Hydrogen is a nonmetal even though it is in group 1.

Worked example

Example 1: Classify from evidence

A student tests four solid samples. Classify each as a metal, nonmetal or metalloid.

A: shiny grey, bends without breaking, bulb lights brightly.
B: yellow, dull, crumbles when pressed, bulb stays off.
C: shiny grey-blue, snaps when bent, bulb glows dimly.
D: reddish, shiny, can be pulled into wire, bulb lights brightly.

A: lustre + malleable + good conductor → metal.
B: dull + brittle + insulator → nonmetal (this matches sulfur).
C: shiny like a metal, but brittle and only a weak conductor → metalloid (this matches silicon).
D: shiny + ductile + good conductor → metal (the reddish colour matches copper).

A and D are metals, B is a nonmetal, and C is a metalloid.

Worked example

Example 2: Predict from position

Selenium (Se) is in period 4, group 16, to the right of the staircase line. Predict three properties of a solid sample of selenium.

To the right of the staircase → nonmetal.
Nonmetal solids are usually dull, brittle and poor conductors of electricity.
Group 16 → 6 valence electrons, so selenium will tend to gain electrons in reactions, like oxygen and sulfur above it.

Selenium should be brittle, a poor conductor and likely to gain electrons. (Some forms of selenium have a slight shine; real elements can surprise you, which is why we test.)

A simple conductivity tester. If the sample conducts electricity, the circuit is complete and the bulb lights.

Properties make elements useful

Copper is ductile and an excellent conductor, so it is used for electrical wiring.
Aluminium has a low density and resists corrosion, so it is used in canoes, ladders and aircraft.
Gold does not corrode, so it is used on electrical contacts and in jewellery.
Silicon is a semiconductor, so it is used in computer chips and solar panels.
Helium is less dense than air and does not burn, so it is used in balloons.
Carbon as graphite is soft and leaves marks, so it is used in pencils ("lead" pencils contain no lead!).

Hands-on activity

Investigate: metal, nonmetal or metalloid?

You need: a grown-up; samples such as aluminium foil, a steel paper clip, a piece of copper wire (from a craft kit or a stripped cable end, prepared by a grown-up), a pencil lead (graphite), a plastic spoon and a metal spoon; a mug of hot tap water; and, if you have one, a simple circuit kit or battery-and-bulb tester (never use a wall outlet).

Safety: wear eye protection when bending things that might snap; hot water can scald, so a grown-up handles it; use only low-voltage batteries (1.5 V to 9 V).

Lustre: look at each sample under a bright light. Shiny or dull?
Malleability: gently bend or press each sample. Does it bend or snap?
Heat conduction: stand the metal spoon and the plastic spoon in the hot water. After 1 minute, carefully touch the handles. Which is warmer?
Electrical conductivity (if you have a tester): touch both wire ends to each sample. Does the bulb light?
Record your results in a table and classify each sample. Which sample surprised you?

What to look for: foil, the paper clip and copper are shiny, bendable and conduct (metals). The metal spoon handle gets warm quickly; the plastic one doesn't. Pencil lead is dull-grey and brittle (nonmetal-like) but conducts electricity: graphite is the well-known exception among nonmetals. Plastic is not an element at all, but it shows what an insulator does.

Just for fun

Gallium is a metal that melts at about 30 °C. Your body is about 37 °C, so a piece of gallium can melt in your hand. (Scientists do this demo with gloves on, since gallium stains skin.)

Your turn

List four physical properties of metals.

Where are the metalloids found on the periodic table?

Why is copper used in electrical wires?

Classify: dull, brittle yellow solid that does not conduct electricity.

Why is hydrogen classified as a nonmetal even though it is in group 1?

What is a semiconductor, and which metalloid is the most famous one?

Which nonmetal conducts electricity, and in what form?

More practice: warm-up

Is iron a metal, nonmetal or metalloid?

Which metal is a liquid at room temperature?

Which nonmetal element is a liquid at room temperature?

What does malleable mean?

Name one metalloid.

More practice: on your own

An element is shiny, brittle and a weak conductor that gets better at conducting when heated. Classify it and explain.

Using valence electrons, explain why metals are found on the left of the table.

Predict two properties of calcium (period 4, group 2).

Why does a metal spoon in hot soup feel hot faster than a wooden spoon?

Aluminium foil and a sheet of paper are both thin and bendable. Give two tests that would show which one is a metal.

Challenge

A newly made element is placed in period 7, group 17. Would you predict it to be a metal or nonmetal based on the staircase? Why might scientists find this hard to test?

Design a fair test to compare how well three metal spoons (steel, aluminium, silver-plated) conduct heat. Name your independent, dependent and controlled variables.

Explain why silicon, a metalloid, is more useful in computer chips than copper, an excellent conductor.

Check your understanding

Quiz

Which property describes most nonmetals that are solids?

Where are metalloids found on the periodic table?

Which element is a metalloid?

A sample is shiny, bends easily and conducts electricity well. It is most likely a...

Why is copper used for electrical wiring?

Which nonmetal can conduct electricity?

For parents and teachers

Big idea: C2.5 asks students to investigate the physical and chemical properties of elements and use their findings to classify elements and identify patterns in the periodic table. The staircase line and the metal / nonmetal / metalloid classification is the first major pattern.

Common difficulties:

Thinking all metals are magnetic. Only a few (iron, nickel, cobalt) are; aluminium and copper are not.
Calling hydrogen a metal because it sits in group 1.
Forgetting exceptions such as mercury (liquid metal), bromine (liquid nonmetal) and graphite (conducting nonmetal).

How to help: supervise the hot water and any wire cutting. If you have a toy circuit kit or a flashlight you can safely open, use its battery and bulb to make a tester. Never let your teen experiment with household (wall-outlet) electricity.