* Is made up of only one type of atom: Silicon is an element, meaning it consists of only silicon atoms.
* Has a consistent composition: Every sample of silicon will have the same chemical makeup and properties. It doesn't contain impurities or other elements.
* Cannot be broken down further by physical means: Silicon is the simplest form of silicon. You can't separate it into simpler substances.
In contrast:
* A mixture like sand is not a pure substance because it contains multiple substances (like silicon dioxide, quartz, and other minerals).
* A compound like silicon dioxide (SiO2) is also not a pure substance in the same way as silicon, although it is a pure compound. This is because it consists of two different elements bonded together.
Therefore, silicon is a pure substance because it's an element, consisting only of silicon atoms, and cannot be further broken down.
