IonicCompounds

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7-4-7-6 Atoms are made of protons, with positive charges, and electrons, with negative charges. When an atom, usually of a metal, loses an electron, it becomes an ion with a positive charge. When an atom of a non-metal gains electrons, it becomes a negative ion. The charge of the ion is determined for metals by subtracting the number of electrons from the number protons and vice versa for non-metals.

Example Sodium (Na) ion with 11 protons and 10 electrons. The net charge is thus:

                                                                                               11 protons....11+
                                                                                              -10 electrons..10-
                                                                                               Net Charge=   +1

Therefore the ion is labled Na⁺¹

Ionic Compounds are formed when ions combine. They are represented by empirical formulas not molecular formulas. For example: Sodium Chloride, made up of Na+ ions and Cl- ions, is represented by the empirical formula NaCl. The formula unit shows the lowest whole number ratio of the ions in the compound. The symbol for an ion concists of the symbol and a superscript showing the charge.

Positive ions formed by metals are called cations. Negative ions formed by nonmetals are called anions. All ionic compounds contain cations and anions in a fixed ratio, in which the charges balance eachother off, making the compound nutral.