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Relative Strengths of Bonds: Bond Strength Rank From Strong to Weak

Ionic bonds are the strongest type of bond. However, a covalent bond is stronger than an ionic bond in certain scenarios.

Only covalent bonds can have different numbers of bonds. A triple bond is stronger than a double bond which is stronger than a single covalent bond.

A hydrogen bond is the weakest type of bond.

(Video) Bond Length and Bond Energy

by Bozeman Science

In this video, you will learn how bond length is related to bond strength. You will also learn about the energy involved in breaking and forming bonds.

Relative Strengths of Bonds

What makes a bond strong?

• Typically, bond strength depends on the number of bonds, the bond energy, the bond length, and the atoms involved.

• Sharing more valence electrons creates multiple bonds.

• Forming multiple bonds between atoms causes them to be pulled closer together. So, we produce a stronger bond.

• The stronger the bond, the more energy required to break the bond.

Bond Strength Between Number of Bonds

Weak: Single Bonds:

• Single bonds share a single pair of electrons between the two atoms.

Moderate: Double Bonds:

• Double bonds share two pairs of electrons between the two atoms.

• Double bonds are shorter than single bonds.

Strong: Triple Bonds

• Triple bonds share three sets of electron pairs.

• Triple bonds are the shortest covalent bond.

Bond Strength Between Types of Bonds

For both ionic and covalent bonds, there is a wide range of bond strengths. It depends on what atoms are involved in the bonding. So, it is difficult to say which type of bond is stronger.

Strong: Ionic bonds

• Ionic bonds are formed due to the attraction between the cationic and anionic ions.

• The electrostatic attraction between the cation and anion is very strong. So, ionic bonds are very hard to break. They are $\underline{generally}$ the strongest bonds.

• Ionic bond strength depends on the ionic charge. For example, an ion with a -2 charge will form a stronger bond than an ion with a -1 charge.

• The ionic radius also affects the strength of ionic bonds. Larger ions form weaker ionic bonds than smaller ions. Why? Because there is a greater distance between the nuclei. They are further apart.

Moderate: Covalent bonds

• Covalent bonds share electrons in order to form a bond. The sharing of electrons causes the nuclei of the atoms to be attracted toward the shared electron pair, which results in a strong bond (strong bonds = harder to break).

• From strongest to weakest: Triple covalent bonds, double covalent bonds, single covalent bonds.

• There are some covalent bonds that are stronger than some ionic bonds. It depends on what we are comparing.

• Polar covalent bonds are stronger than nonpolar covalent bonds. Polar covalent bonds are between atoms with different electronegativities. So the more electronegative atom pulls the electrons towards itself. There is more electrostatic attraction between the partial charges. A polar covalent bond has some ionic characteristics. So, it's stronger than a nonpolar bond.

Weak: Intermolecular Forces

• Van der Waal's forces are a form of electrostatic attraction. But, they don't compare to actual bonds.

• Ion-dipole forces are the strongest interaction. Why? The presence of an ion gives the interaction a slight ionic character.

• Dipole-dipole interactions are the second strongest intermolecular force.

• Dipoles are partial charges located at the poles of a molecule. The dipole is created by the electronegativity difference and the molecular geometry. The positive pole is attracted to areas of high electron density on other molecules.

• Hydrogen bonds are the strongest dipole-dipole interaction. They are formed between hydrogen atoms and a highly electronegative atom (nitrogen, oxygen, or fluorine).

• Dispersion forces are the weakest intermolecular interaction.

• Dispersion forces are caused by the random movement of electrons. In the quantum mechanical model, it's rare for electrons to be evenly distributed in an orbital. The uneven distribution creates temporary dipoles.