KEY2CHEM

Types of Chemical Bonds

The type of chemical bond formed between two atoms depends on the nature of each atom in the bond. Ionic bonds generally form between a metal and a nonmetal and result from a transfer of an electron from the metal to the nonmetal. Covalent bonds generally form between nonmetals and result from a sharing of electrons between the atoms. Metallic bonds generally form between metallic atoms, with the valence electrons delocalized in a “sea” around the metallic cations.

Example 1.

What is the major type of bonding in $$\require{mhchem}\ce{NaCl}$$?

A. ionic

B. covalent

C. metallic

Solution

A. ionic

Sodium is a metal and chlorine is a nonmetal. As such, ionic bonding is expected to be the major type of bonding interaction between these particles.

Example 2.

What is the major type of bonding in $$\require{mhchem}\ce{Ag(s)}$$?

A. ionic

B. covalent

C. metallic

Solution

C. metallic

In a metal, such as $$\require{mhchem}\ce{Ag}$$, the valence electrons are delocalized in an “electron sea” surrounding the metallic $$\require{mhchem}\ce{Ag}$$ cores (nuclei plus inner electrons).

Example 3.

What is the major type of bonding in $$\require{mhchem}\ce{H2O}$$?

A. ionic

B. covalent

C. metallic

Solution

B. covalent

Hydrogen and oxygen and both nonmetals, so covalent bonds are expected to form. Because hydrogen and oxygen have different electronegativity values, the $$\require{mhchem}\ce{H-O}$$ bonds in water are polar covalent bonds (unequal sharing of electrons).