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Primary Bond Types: There are 3 major types of primary bonds--ionic, covalent, and metallic--which reflect the 3 different ways that you can combine the two major types of elements,metals and nonmetals.

Remember that metals are elements that have a relatively weak attraction for their outermost electrons, while nonmetals are elements with a strong attraction for these electrons. As you move to the left and down on the Periodic Table, elements get 'more metallic'; as you move to the right and up, elements get 'more nonmetallic'.


Bond Type	Elements	Example


Ionic	Metal + Nonmetal	NaCl (table salt)


Covalent	Nonmetal + Nonmetal	H₂O (water)

Metallic	Metal + Metal	Fe (iron)

Ionic: Metal + Nonmetal

Electrons are transferred from the metal to the nonmetal, creating positively charged cations and negatively charged anions.
Ionic materials are usually brittle solids at room temperature, and they exist as highly-ordered 3-dimensional arrangements of vast numbers of ions. The exact proportions of the different types of ions are given by the compound's chemical formula, and reflect a balance of total positive and negative charges.
Most geological minerals are ionic compounds.

Covalent: Nonmetal + Nonmetal

Electrons are shared between pairs of nonmetal atoms, each of which has a relatively strong attraction for those electrons.
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Covalently bonded materials come in 2 major types--molecular substances and covalent network solids (or covalent crystals).

Molecular substances: Most covalent substances exist as molecules , which are small to medium-sized groups of atoms connected by covalent bonds. Because a molecule is attracted to other molecules in the sample by weaker secondary bonds, most molecular substances exist as gases or liquids at room temperature. The nature of the attraction between molecules depends a great deal on the way that the atoms in the molecule are arranged (i.e., on the molecular shape).
Since the strength of secondary bonds tends to go up with molecular size, larger molecules can exist as solids, but they usually have low melting points and poor mechanical strength. Waxes, polymers (plastics), and many biological tissues are all familiar examples of large molecular substances.

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