Chemical Bonding and Material Attributes

Fundamental Chemical Definitions

Molecule

The union of atoms.

Lattice

A continuous structure of millions of atoms.

Chemical Bond

The attractive force that keeps atoms united in a molecule or a crystal.

Elementary Chemical Substance

Atoms of the same element that unite.

Chemical Compound

Atoms of different elements that unite.

The Octet Rule

Atoms of different chemical elements tend to join with other atoms to have eight electrons in their outermost shell, known as an octet, to achieve greater stability.

Types of Chemical Bonds

Ionic Bond

The transfer of valence electrons. The ionic bond is the union of oppositely charged ions through electrostatic forces of attraction. In this case, the elements bond to achieve a noble gas electron configuration.

Ionic Crystal

A structure where each negative ion is surrounded by positive ions, and these ions, in turn, by negative ions.

Empirical Formula

Indicates the proportion of each type of ion in the ionic crystal.

Molecular Formula

Indicates the exact number of each type of atom that exists in the molecule.

Properties of Ionic Substances

• Are solid at room temperature and melt at elevated temperatures.
• Are hard but brittle.
• Their water solubility is highly variable.
• Do not conduct electricity in solid form but do when melted or in solution.

Covalent Bond

The union of atoms through the sharing of valence electrons. In this case, the elements bond to achieve a noble gas electron configuration.

Properties of Molecular Substances (Covalent)

• They have low melting and boiling points, and at room temperature, they are often gases.
• In the solid state, they have a low density.
• Some are soluble in water and in other solvents.
• Are not electrical conductors.

Atomic Crystal

An orderly and continuous structure of atoms united by covalent bonds.

Properties of Atomic Substances

• Are solid, dense, and very hard.
• Are insoluble in any solvent.
• Do not conduct electricity.

Metallic Bond

Occurs between metal atoms that release electrons and acquire a positive charge.

Metallic Lattice

A giant three-dimensional structure.

Properties of Metals

• Their brightness is due to the electron cloud.
• Most are dense solids or liquids.
• Are ductile and malleable.
• Are insoluble in any solvent.
• Are very good thermal and electrical conductors.

Alloys

These are solutions in which one or more metals are dissolved in another metal.