Question

Which is stronger: the covalent bond that holds atoms together within a molecule or the electrical attraction between two neighboring molecules?

Short answer

Covalent bonds are stronger than intermolecular forces.

Step-by-step solution

Introduction to Bond Types

To compare bond strength, let’s first understand the two types of bonds involved. A covalent bond arises when two atoms share electrons, resulting in a very strong connection within a molecule. Meanwhile, the electrical attraction between two neighboring molecules is often due to intermolecular forces such as van der Waals forces or hydrogen bonds, which are generally weaker.

Understanding Covalent Bonds

Covalent bonds involve shared electrons between atoms within a molecule. These bonds require significant energy to break due to the sharing of electrons, creating a stable molecular structure. Their strength is generally measured in hundreds of kilojoules per mole.

Exploring Intermolecular Forces

Intermolecular forces refer to attractions between molecules. Common types include dipole-dipole interactions, hydrogen bonding, and van der Waals forces. These interactions are weaker than covalent bonds, typically measured in single to tens of kilojoules per mole, and play significant roles in the physical properties of substances like boiling and melting points.

Comparing Bond Energies

By comparing the energies associated with each type of bond, we can determine that covalent bonds, with energies in the hundreds of kilojoules per mole, are significantly stronger than the intermolecular forces, whose energies are much lower by one or two orders of magnitude.

Key concepts

Covalent Bonds

Covalent bonds are a fundamental type of chemical bond where two atoms share pairs of electrons to achieve a more stable electron configuration. This sharing allows each atom to attain the electronic structure of the nearest noble gas, leading to a stable chemical compound. Covalent bonds are extremely strong compared to many other types of bonds. Their strength is due to the overlap of atomic orbitals, which involves the sharing of electrons.
The number of shared electron pairs between the atoms determines the bond type:

• Single bond: one pair of electrons shared
• Double bond: two pairs of electrons shared
• Triple bond: three pairs of electrons shared

These bonds are typically measured in hundreds of kilojoules per mole, signifying high energy requirements to break them, which is why they maintain the integrity of the molecule under normal conditions.

Intermolecular Forces

Intermolecular forces are forces of attraction or repulsion which act between neighboring particles (atoms, molecules, or ions). These forces are much weaker than covalent bonds because they do not involve sharing of electrons. Instead, intermolecular forces arise due to attractions between partial positive and negative charges within or between molecules.
There are several types of intermolecular forces:

• Dipole-Dipole Interactions: Occur between polar molecules, where the positive pole of one molecule attracts the negative pole of another molecule.
• Hydrogen Bonds: A special, stronger type of dipole-dipole interaction, occurring when hydrogen is bonded to electronegative elements like oxygen, nitrogen, or fluorine.
• Van der Waals Forces: Weak forces that arise from temporary dipoles induced in atoms or molecules.

These forces generally range from a few to tens of kilojoules per mole, much lower than the energy required to break covalent bonds. However, they play essential roles in dictating the physical properties of substances, such as boiling and melting points.

Bond Strength

Bond strength refers to the amount of energy required to break a bond. In the realm of chemical bonds, it is vital to differentiate between the strength of intramolecular and intermolecular forces.

• Intramolecular Bonds: These include covalent bonds, which hold atoms together within a molecule. They are much stronger and typically measured in the hundreds of kilojoules per mole. The energy required to break such bonds is substantial, reflecting their stability and resistance to chemical change.
• Intermolecular Forces: Conversely, these forces govern the interactions between molecules, such as hydrogen bonds and van der Waals forces. Despite being significantly weaker, they are crucial for physical properties.

In conclusion, covalent bonds are significantly stronger than intermolecular forces. This distinction helps explain why molecules maintain their structure while requiring lower energy for processes like boiling or melting that involve separating molecules rather than altering their internal structure.