Elements, Compounds, Symbols and Formulae

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An element is a pure substance made up of only one kind of atom. It cannot be broken down into simpler substances by physical or chemical means. Example: Oxygen (O), Iron (Fe).

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A compound is a pure substance formed when two or more different elements combine chemically in a fixed proportion by mass. Example: Water (H₂O) is made of hydrogen and oxygen.

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The symbol for sodium is 'Na'. It comes from its Latin name 'Natrium'. Many element symbols are derived from their Latin names.

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The molecular formula of water is H₂O. This means one molecule of water contains 2 atoms of hydrogen and 1 atom of oxygen bonded together.

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Metals are elements that are usually shiny, hard, good conductors of heat and electricity, and can be drawn into wires or beaten into sheets. Examples: Iron (Fe), Copper (Cu).

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Non-metals are elements that are generally dull, poor conductors of heat and electricity, and brittle. Examples: Carbon (C), Oxygen (O).

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An atom is the smallest particle of an element that retains its properties. A molecule is the smallest particle of a compound (or element) that can exist independently. For example, O is an oxygen ato…

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Atomicity is the number of atoms present in one molecule of an element. Example: Oxygen (O₂) has atomicity 2; Ozone (O₃) has atomicity 3.