How to read chemical formulas

SYMBOLS, FORMULAS AND EQUATIONS

Read the text and learn how to read chemical formulas.

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 is He, of copper is Cu, of sodium is Na, of plutonium is Pu. Groups of symbols are called formulas. They are used to designate compounds. The formulae 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)

The symbols of chemical elements are read according to the names of English alphabet letters.

The sign “+” is read as plus, and, together, with, react with.

The sign “-“ indicates one relation and isn't read at all.

The sign “=” is read as give, form or produce.

The sign “ “ is read as give, pass over to or lead to.

The sign “ ” is read as forms and is formed from.

2H₂O – a figure before an element signifies the number of molecules; two molecules of water.

2H₂+O₂ 2H₂O

Two molecules of H two plus O two give two molecules of H two O or Two two-atom molecules of hydrogen react with one two-atom molecule of oxygen and produce two molecules of water.

N₂+3H₂ 2NH₃

N two plus three molecules of H two form and are formed from two molecules of NH three or one two-atom molecule of nitrogen plus three two-atom molecules of hydrogen form and are formed from two molecules of ammonia.

Na₂CO3+CaSO₄ Na₂SO₄+CaCO₃

Na two Co three plus CaSO four form Na two SO four plus CaCO three or the sodium (Na) and the calcium (Ca) switch places. The sodium combines with the sulphate radical (SO₄), forming sodium sulphate (Na₂SO₄) which dissolves in water. The calcium combines with the carbonate radical (CO₃), forming calcium carbonate (CaCO₃). Calcium carbonate does not dissolve in water and so settles to the bottom of the solution.

Дата добавления: 2014-11-07