Question

Define the following terms: element, compound, molecule, symbol and formula.

Answer 1

Element: Element is a pure chemical substance consisting of same type of atoms, and it cannot be broken down into simpler components by chemical means. Example: oxygen, calcium, iron, gold and mercury.

Compound: Compound is a pure chemical substance consisting of two or more different chemical elements. For example, water (H₂O) is a compound made up of two elements, hydrogen and oxygen.

Molecule: Molecule is the smallest particle of a substance (element or compound) that retains the physical and chemical properties of that substance and can stand on its own. Molecule of an element is composed of one or more atoms of same kind. For example, H₂ is the molecule of hydrogen element formed from two hydrogen atoms. Molecule of a compound is composed of two or more atoms of different elements. For example, water is a molecule of compound composed of two atoms of hydrogen element and one atom of oxygen element.

Symbol: An element is represented by one or two letter code known as its chemical symbol usually derived from the first two letters of the name of the element, often in Latin, where only the first letter is capitalised. For example, symbol of aluminium is Al. Potassium has the symbol K derived from its Latin name kalium.

Formula: Formula represents the number of atoms of each kind of element that combine to make one molecule an element or a compound. For example, formula of sodium chloride is NaCl. It represents one molecule of sodium chloride containing one atom of sodium and one atom of chlorine. Similarly, formula of oxygen element is O₂. It represents one molecule of oxygen formed from two atoms of oxygen.