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 consists 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 neutral. 12@@3