Structure of the Periodic Table
3. Metals, Non-Metals, and Metalloids
Learning outcomes
- I can identify the locations of metals, non-metals, and metalloids on the periodic table.
- I can compare the physical and chemical properties of metals and non-metals.
- I can describe the characteristic properties of metalloids.
- I can explain how the properties of elements influence their practical uses.
- I can classify unfamiliar elements as metals, non-metals, or metalloids using provided information.
Metals, Non-Metals, and Metalloids
The elements on the periodic table can be divided into three broad categories: metals, non-metals, and metalloids.
An element's location on the periodic table provides useful clues about its properties. These properties also help determine how different elements are used in everyday life, technology, construction, medicine, and industry.
Where Are Metals, Non-Metals, and Metalloids?
The three categories occupy different regions of the periodic table.
- Metals are found mainly on the left and centre.
- Non-metals are found mainly on the right side.
- Metalloids are found along the zigzag or staircase line separating metals and non-metals.
There is one important exception: hydrogen is located on the left side of the periodic table but is a non-metal.
Metals
Most elements on the periodic table are metals.
Common examples include:
- iron (Fe)
- copper (Cu)
- aluminium (Al)
- sodium (Na)
- calcium (Ca)
- gold (Au)
- silver (Ag)
Although metals do not all behave exactly the same way, they share several characteristic physical properties.
Physical Properties of Metals
Metals are generally:
- shiny when freshly cut or polished
- good conductors of electricity
- good conductors of thermal energy
- malleable – they can be hammered or pressed into different shapes
- ductile – they can be drawn into wires
- strong and dense
- solid at room temperature
There are exceptions. For example, mercury (Hg) is a metal but is liquid at room temperature.
Chemical Properties of Metals
During chemical reactions, metal atoms often lose electrons.
When an atom loses electrons, it forms a positive ion, called a cation.
For example, sodium can lose one electron:
Na → Na⁺ + electron
Magnesium can lose two electrons:
Mg → Mg²⁺ + 2 electrons
Many metals also react with other substances.
For example:
Metal + oxygen → metal oxide
Some metals can also react with acids:
Metal + acid → salt + hydrogen gas
However, metals vary greatly in their reactivity. Potassium and sodium are very reactive, while metals such as gold are much less reactive.
Non-Metals
Non-metals occupy a much smaller region of the periodic table.
Examples include:
- hydrogen (H)
- carbon (C)
- nitrogen (N)
- oxygen (O)
- phosphorus (P)
- sulfur (S)
- chlorine (Cl)
Non-metals can exist as solids, liquids, or gases at room temperature.
For example:
- carbon is a solid
- bromine is a liquid
- oxygen is a gas
Physical Properties of Non-Metals
Solid non-metals are generally:
- dull rather than shiny
- poor conductors of electricity
- poor conductors of thermal energy
- brittle rather than malleable
- not ductile
- often less dense than metals
Again, there are exceptions. For example, graphite, a form of carbon, can conduct electricity even though carbon is a non-metal.
Chemical Properties of Non-Metals
Non-metal atoms often gain electrons or share electrons when they form chemical bonds.
For example, chlorine can gain one electron:
Cl + electron → Cl⁻
The chlorine atom becomes a negatively charged chloride ion.
Non-metals can also share electrons with other non-metals to form covalent bonds.
For example, hydrogen and oxygen share electrons when they form water molecules.
Comparing Metals and Non-Metals
There are several important differences between the typical properties of metals and non-metals.
| Property | Metals | Non-Metals |
|---|---|---|
| Appearance | Usually shiny | Usually dull |
| Electrical conductivity | Good | Usually poor |
| Thermal conductivity | Good | Usually poor |
| Malleability | Usually malleable | Usually brittle if solid |
| Ductility | Usually ductile | Usually not ductile |
| State at room temperature | Mostly solids | Solids, liquids or gases |
| Electron behaviour | Often lose electrons | Often gain or share electrons |
| Ions commonly formed | Positive | Negative |
These are general patterns, not rules without exceptions.
Metalloids
Between the metals and non-metals is a small group of elements called metalloids.
Metalloids have properties that are intermediate between metals and non-metals.
Commonly recognised metalloids include:
- boron (B)
- silicon (Si)
- germanium (Ge)
- arsenic (As)
- antimony (Sb)
- tellurium (Te)
The exact classification of a few elements near the staircase can vary between sources.
Properties of Metalloids
Metalloids may:
- have a metallic or shiny appearance
- be brittle like non-metals
- conduct electricity better than most non-metals
- conduct electricity less effectively than typical metals
- behave chemically like metals in some situations and non-metals in others
One particularly important property is their ability to act as semiconductors.
What Is a Semiconductor?
A semiconductor is a material whose electrical conductivity lies between that of a conductor and an insulator.
This property can be carefully controlled, making semiconductors extremely useful in electronics.
Silicon is one of the most important examples.
Silicon is used to manufacture:
- computer chips
- smartphones
- electronic sensors
- calculators
- solar cells
- many other electronic devices
Suggested placement: Silicon wafers or microchips make a strong visual connection between metalloids and modern technology.
Properties Determine Uses
Scientists and engineers select materials because of their properties.
The properties of an element determine whether it is suitable for a particular job.
Copper – Electrical Wiring
Copper is an excellent electrical conductor and can be drawn into thin wires.
Therefore, copper is widely used in:
- electrical cables
- motors
- electronics
Aluminium – Aircraft and Transport
Aluminium has a relatively low density and is resistant to corrosion.
It is therefore useful for:
- aircraft
- vehicles
- drink cans
- window frames
Iron – Construction
Iron is used to produce steel, which can be very strong.
Steel is widely used in:
- buildings
- bridges
- vehicles
- machinery
Silicon – Electronics
Silicon is a semiconductor, allowing its electrical behaviour to be carefully controlled.
It is therefore essential for many electronic components.
Oxygen – Medicine and Respiration
Oxygen is a reactive non-metal gas required for aerobic respiration.
It is used in:
- medical oxygen systems
- breathing equipment
- industrial processes
This gives us an important relationship:
Structure → Properties → Uses
The atomic structure of an element influences its properties, and those properties influence how the element can be used.
Classifying an Unfamiliar Element
Even if we do not know the name of an element, we may be able to classify it from information about its properties.
Example 1
An unknown element:
- is shiny
- conducts electricity
- can be hammered into sheets
- forms positive ions
These are typical properties of a metal.
Example 2
Another element:
- is dull
- is brittle when solid
- does not conduct electricity well
- tends to gain electrons
These properties suggest a non-metal.
Example 3
A third element:
- is shiny
- is brittle
- conducts electricity moderately well
- is used in electronic components
This combination suggests a metalloid.
When classifying an unfamiliar element, look for several pieces of evidence rather than relying on only one property.
Did You Know?
More than three-quarters of the known elements are metals.
However, some of the elements most important to living organisms are non-metals. Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur are all non-metals and are essential components of living things.
Key Terms
Metal – An element that generally conducts heat and electricity well and tends to lose electrons during reactions.
Non-metal – An element that generally conducts heat and electricity poorly and tends to gain or share electrons.
Metalloid – An element with properties intermediate between those of metals and non-metals.
Malleable – Able to be hammered or pressed into different shapes without breaking.
Ductile – Able to be drawn into a wire.
Brittle – Likely to break or shatter rather than bend.
Conductor – A material that allows thermal energy or electricity to pass through easily.
Semiconductor – A material with electrical conductivity between that of a conductor and an insulator.
Key Takeaways
- Metals are located mainly on the left and centre of the periodic table.
- Non-metals are located mainly on the right side, with hydrogen as an important exception.
- Metalloids occur along the staircase between metals and non-metals.
- Metals are generally shiny, malleable, ductile, and good conductors.
- Non-metals are generally poor conductors and are often brittle when solid.
- Metals often lose electrons, while non-metals often gain or share electrons.
- Metalloids have a mixture of metallic and non-metallic properties.
- Some metalloids, especially silicon, are important semiconductors.
- The properties of elements determine their practical uses.
- The properties and periodic-table position of an unfamiliar element can provide evidence for classifying it as a metal, non-metal, or metalloid.