Question

What is a coordinate covalent bond? Is it different from an ordinary covalent bond?

Short answer

A coordinate covalent bond is formed when one atom donates both electrons to a bond, unlike regular covalent bonds where each atom donates one electron.

Step-by-step solution

Define a Covalent Bond

A covalent bond is a type of chemical bond where two atoms share a pair of electrons. This shared pair of electrons allows each atom to attain the electron configuration of a noble gas, typically resulting in a more stable molecular structure.

Define a Coordinate Covalent Bond

A coordinate covalent bond (or dative bond) occurs when one atom provides both electrons for a shared electron pair that constitutes the bond. This usually happens when one atom has a lone pair of electrons, and the other atom has vacant orbitals to accept the pair.

Compare Covalent and Coordinate Covalent Bonds

In a regular covalent bond, each atom contributes one electron to the electron pair that forms the bond. In contrast, in a coordinate covalent bond, one atom donates both electrons that are shared in the bond. Despite the difference in how the bonds are formed, once established, coordinate covalent bonds are often indistinguishable from ordinary covalent bonds.

Key concepts

Covalent Bond

A covalent bond is an essential concept in chemistry, pivotal to understanding how molecules form. When two atoms share a pair of electrons, they create a covalent bond. This sharing allows each atom to reach a more stable electron configuration, often resembling that of a noble gas. See how atoms in a hydrogen molecule (H₂) share electrons, achieving stability similar to helium. Covalent bonds form when atoms have similar electronegativities. These bonds are not just chemical connections; they define the structure and properties of molecules in a fundamental way. Covalent bonds can be single, double, or triple, depending on how many pairs of electrons are shared between the atoms:

• Single bond: One pair of shared electrons.
• Double bond: Two pairs of shared electrons.
• Triple bond: Three pairs of shared electrons.

Understanding this concept helps explain everything from the flexibility of molecules to why water is a liquid at room temperature.

Electron Sharing

Electron sharing is the hallmark of covalent bonding. In covalent bonds, atoms achieve more stable configurations by sharing electrons. While ionic bonds involve the transfer of electrons, covalent bonding is all about sharing to fulfill the octet rule. The way atoms share electrons affects molecular properties:

• Balanced sharing: Results in nonpolar covalent bonds, like in O₂, where sharing is equal.
• Unequal sharing: Leads to polar covalent bonds, such as in H₂O, where electrons are drawn more to one atom.

This subtle difference in sharing results in varied molecular interactions and behaviors.

Lone Pairs

Lone pairs are non-bonding electrons present on an atom within a molecule. They don't participate in forming bonds but are crucial in defining a molecule's shape and chemical reactivity. Consider the water molecule (H₂O). Oxygen has two lone pairs of electrons, affecting water's bent molecular geometry. Lone pairs are necessary for forming coordinate covalent bonds. When an atom with a lone pair meets another atom that needs additional electrons, it can donate its lone pair to form a stable structure. Lone pairs usually:

• Occupy more space around the atom than bonding pairs.
• Influence the three-dimensional shape and bond angles of molecules.
• Make molecules reactive sites for chemical reactions.

Thus, although lone pairs don't form bonds, their impact on a molecule's behavior is significant.

Molecular Structure

Molecular structure describes the three-dimensional arrangement of atoms within a molecule. Covalent bonding and electron pairs largely determine this structure. The arrangement of atoms affects a molecule's size, shape, and physical properties. Different factors influence molecular structure:

• Bond angles: These angles between bonds relate directly to the type and number of bonds and lone pairs.
• Lone pairs and bonds: Affect the molecule's geometry, exemplified by the VSEPR theory, which predicts molecular shapes based on repulsions between electron clouds.
• Hybridization: Determines overlapping orbitals and influences molecular geometry.

The molecular structure impacts a molecule's physical properties, like boiling and melting points, solubility, and reactivity. Therefore, understanding molecular structure is key to predicting how molecules interact and behave.