Covalent Bonds and Structures

Study Notes

Covalent Bonds

Covalent bonds form by sharing electrons. This sharing allows each atom to achieve a stable electron configuration, often the octet rule.
The shared electrons are attracted to the nuclei of both atoms, holding them together.
Covalent bonds typically occur between non-metal atoms.
Bond strength varies depending on the type and number of atoms involved (e.g., single, double, or triple bonds).
Polar covalent bonds occur when atoms with different electronegativities share electrons unequally, creating partial positive and negative charges.
Nonpolar covalent bonds occur when atoms with similar electronegativities share electrons equally.

Giant Covalent Structures

Giant covalent structures, also known as macromolecules, are composed of a large number of atoms covalently bonded together in a continuous network or lattice.
These structures have high melting and boiling points due to the strong covalent bonds throughout the entire structure.
They are typically hard and brittle because breaking the network requires overcoming numerous very strong bonds.
They are often poor conductors of electricity because the electrons are localized within the bonds.
Examples of giant covalent structures include diamond, graphite, and silicon dioxide (quartz).

Diamond

Each carbon atom in diamond is bonded to four other carbon atoms in a tetrahedral arrangement.
Diamond has a very high melting point and is extremely hard due to the strong covalent bonds.
Diamond is an electrical insulator due to the lack of free electrons.

Graphite

Each carbon atom in graphite is bonded to three other carbon atoms in a layered hexagonal arrangement.
The layers are held together by weak van der Waals forces.
This allows the layers to slide over each other, giving graphite its slippery feel and making it a good lubricant.
Graphite conducts electricity because delocalized electrons are free to move between the layers.

Silicon Dioxide (Quartz)

Silicon dioxide (SiO₂) is a giant covalent structure where each silicon atom is bonded to four oxygen atoms, and each oxygen atom is bonded to two silicon atoms.
This structure forms a continuous network of SiO₄ tetrahedra.
Silicon dioxide has a high melting point and is hard.
It is an electrical insulator.

Properties of Giant Covalent Structures Summary

High melting and boiling points: Strong covalent bonds throughout the structure require a lot of energy to break.
Hardness and brittleness: A large network of strong covalent bonds; breaking the structure requires overcoming many bonds, resulting in a brittle material.
Poor electrical conductivity: Electrons are localized within the bonds and are not free to move; exceptions include graphite, which exhibits conductivity due to delocalized electrons.
Insoluble in water: Primarily because of the strength of the covalent bonds.

Description

This quiz covers the basics of covalent bonds, including their formation, types, and characteristics, as well as the concept of giant covalent structures. Explore how atoms share electrons and the implications of polar and nonpolar bonds in various compounds.