3. SYMBOLS, FORMULAS AND EQUATIONS

3. SYMBOLS, FORMULAS AND EQUATIONS

Each of the 107 presently known chemical elements has a symbol. This symbol is usually derived from the name of the element. The symbol of oxygen is O, of hydrogen is H, of helium, He, of copper, Cu, of sodium, Na, of plutonium, Pu. Groups of symbols are called formulas. They are used to designate compounds. The formula for water is H₂O, for carbon dioxide CO₂, for sulphuric acid H₂SO₄. These symbols and formulas are used to indicate chemical reactions. For example:

2H₂O = 2H₂ + O₂

(Statement: Water decomposes to form hydrogen and oxygen)