Types of Chemical Bonds Explained

Click through each step to understand the basics.

How Ionic Bonds Work
An ionic bond forms when a metal atom loses electrons to become a positive ion and a nonmetal atom gains those electrons to become a negative ion, and the oppositely charged ions attract each other electrostatically. Table salt (sodium chloride, NaCl) is the classic example, where sodium gives up one electron and chlorine accepts it.
How Covalent Bonds Work
A covalent bond forms when nonmetal atoms share electrons with each other to achieve a stable electron configuration. A water (H₂O) molecule is a classic covalently bonded substance, formed when an oxygen atom shares an electron pair with each of two hydrogen atoms.
Metallic Bonds and the Properties of Metals
A metallic bond forms when the electrons released by metal atoms move freely rather than belonging to any single atom, creating a 'sea of electrons' that holds the metal cations together. This sea of free electrons is why metals conduct electricity and heat well, and why they can be hammered or stretched without breaking (malleability and ductility).
How Bond Type Determines a Substance's Properties
Ionically bonded substances generally have high melting points and don't conduct electricity as solids, but conduct well when dissolved in water or melted. Covalently bonded substances tend to have relatively low melting points and don't conduct electricity well — so bond type alone can predict several properties of a substance.
The Octet Rule
Most atoms tend to fill their outermost electron shell with 8 electrons to achieve a stable configuration like a noble gas, a tendency known as the octet rule. Ionic bonds satisfy this by fully transferring electrons, while covalent bonds satisfy it by sharing electrons.
Polar vs. Nonpolar Covalent Bonds
When identical atoms bond, they attract electrons equally, forming a nonpolar covalent bond; but when atoms with different electronegativity bond, electrons are pulled more toward one side, forming a polar covalent bond. A water molecule is polar because oxygen attracts electrons more strongly than hydrogen.
The Difference From Intermolecular Forces
Unlike the chemical bonds that hold atoms together within a molecule, the weaker forces of attraction that act between separate molecules are called intermolecular forces, with hydrogen bonding being a classic example. Water's unusually high boiling point compared to similarly sized molecules is due to the relatively strong hydrogen bonding between water molecules.

Why Learn About Chemical Bonds?

Why salt dissolves easily in water and conducts electricity while sugar dissolves but doesn't conduct electricity, and why metal can be hammered into new shapes — these all come down to differences in how atoms bond together. Understanding the types of chemical bonds lets you logically predict a substance's properties, like melting point, conductivity, and solubility.

Covalent Bonds in Carbon-Based Organic Compounds Are Worth Exploring Too

Covalent bonding, in particular, creates a huge diversity of structures in organic compounds built around carbon — a related topic worth exploring separately, covering the world of compounds built on a carbon backbone.

Frequently Asked Questions

Can a single molecule contain more than one type of bond?

Yes, it's possible. For example, in calcium carbonate (CaCO₃), the calcium ion and carbonate ion are connected by an ionic bond, but the carbon and oxygen within the carbonate ion itself are connected by covalent bonds.

What's an easy way to tell ionic and covalent substances apart?

Generally, a metal bonding with a nonmetal tends to form an ionic bond, while two nonmetals bonding tends to form a covalent bond. Also, a substance that's solid at room temperature and conducts electricity well when dissolved in water is likely ionically bonded.