Predicting ionic charges
Many atoms gain or lose electrons such that they end up with the same number of electrons as the noble gas closest to them in the periodic table.
The noble gasses are generally chemically non-reactive, they would appear to have a stable arrangement of electrons.
Other elements must gain or lose electrons, to end up with the same arrangement of electrons as the noble gases, in order to achieve the same kind of electron stability.
Example: Nitrogen
Nitrogen has an atomic number of 7; the neutral Nitrogen atom has 7 protons and 7 electrons. If Nitrogen gained three electrons it would have 10 electrons, like the Noble gas Neon (10 protons, 10 electrons). However, unlike Neon, the resulting Nitrogen ion would have a net charge of N3- (7 protons, 10 electrons).
The location of the elements on the Periodic table can help in predicting the expected charge of ionic forms of the elements.
This is mainly true for the elements on either side of the chart.
Ionic compounds
Ions form when one or more electrons transfer from one neutral atom to another. For example, when elemental sodium is allowed to react with elemental chlorine an electron transfers from a neutral sodium to a neutral chlorine. The result is a sodium ion (Na+) and a chlorine ion, chloride (Cl-):
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The oppositely charged ions attract one another and bind together to form NaCl (sodium chloride) an
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