The electrons in an atom are arranged in Shells around the nucleus. These shells are also known as electron Orbital or Energy Levels.
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Atomic Bonding:
Other then the NOBLE GASES, the atoms of all other elements have incomplete outer shells. That is why they react. For any atom to become stable it must have its outer shell full of electrons 8 of the with the exception of Hydrogen and Helium, which only require 2 electrons. They can do this in two different ways:
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By losing or gaining electrons or - ionic bonding
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By sharing electrons - covalent bonding
Ionic Bonding - it is all about atoms losing or gaining electrons to become stable, i.e. (have their outer shell full of electrons).
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Remember ! A full outer shell makes an atom stable.
Some facts:
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During ionic bonding, atoms gain or lose electron(s) to form stable negatively (-Ve) or positively (+Ve) charged ions which are then strongly attracted to one another to form an IONIC BOND.
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Ionic bonds form between metals and non-metals.
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Most metallic elements lose electrons to form a POSITIVE ION.
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Most non-metallic elements gain electrons to form a NEGATIVE ION.
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An ION is a charged particle (not an atom any more). It is charged because it contains an unequal number of protons and electrons.
Let's look at sodium chloride as an example: