In basic general science, which one of the following substances is not a metal, while the others listed are typical metals?

Introduction / Context:
Identifying metals and non-metals is one of the first skills taught in basic chemistry and general science. Metals have properties such as lustre, malleability, ductility, and good electrical and thermal conductivity, while non-metals often lack these traits and may be brittle or gaseous. This question asks which one of the listed substances is not a metal, testing your ability to recognise a common non-metal among everyday metallic elements.

Given Data / Assumptions:
- The options include iron, copper, sulphur, and aluminium. - Three of these are well-known metals used in industry and daily life. - One is a non-metal that does not exhibit typical metallic properties. - We assume standard periodic table classifications.

Concept / Approach:
Iron, copper, and aluminium are all typical metallic elements found on the left and central parts of the periodic table. They are solid at room temperature, shiny when polished, malleable, and good conductors of heat and electricity. Sulphur, however, is a non-metal located in the p-block and exists as a brittle yellow solid at room temperature; it is a poor conductor and lacks metallic lustre. The approach is to identify the odd one out based on these physical and chemical characteristics.

Step-by-Step Solution:
Step 1: Consider iron. It is widely used in construction and engineering and is a typical metal with high strength and good conductivity. Step 2: Consider copper. It is a reddish metal known for excellent electrical and thermal conductivity and is used in electrical wiring and plumbing. Step 3: Consider aluminium. It is a light, silvery metal used in aircraft, packaging, and many structural applications. Step 4: Consider sulphur. It is a yellow, brittle, non-metallic solid that is not malleable or ductile and is a poor conductor of heat and electricity. Step 5: Based on these properties, sulphur clearly stands out as the non-metal, while the other three are metals.

Verification / Alternative check:
The periodic table lists iron (Fe), copper (Cu), and aluminium (Al) as metallic elements. They are located in regions associated with metals and form positive ions (cations) in many of their compounds. Sulphur (S) is located among the non-metals and typically forms negative ions (anions) such as sulphide (S^2-) in ionic compounds. It also forms covalent compounds like sulphur dioxide and sulphuric acid. These periodic table positions and chemical behaviours confirm that sulphur is a non-metal while the others are metals.

Why Other Options Are Wrong:
Iron (option a) is unmistakably a metal, used extensively for making steel and other alloys. Copper (option b) is a classic metal used in conductors and heat exchangers. Aluminium (option d) is a lightweight metal widely employed where low density and corrosion resistance are important. None of these substances fits the description of a non-metal, so they cannot be the correct answer to a question asking which one is not a metal.

Common Pitfalls:
Some learners may be unfamiliar with sulphur in its elemental form and focus mainly on metal uses, leading them to overthink the question. Another pitfall is confusing metalloid and non-metal categories, but sulphur is clearly categorised as a non-metal, not a metalloid like silicon. Remembering basic periodic table groups and the common physical appearance of sulphur as a yellow, brittle substance will help you quickly identify it as the non-metal among the choices.

Final Answer:
The substance that is not a metal is sulphur, a non-metallic element.