Covalent Bonding and Allotropes of Carbon

A comprehensive set of flashcards covering the topics of covalent bonding, simple molecular substances, polymers, giant covalent substances, and allotropes of carbon for effective exam preparation.

What is covalent bonding?

Covalent bonding is the sharing of pairs of electrons between non-metal atoms to achieve a full outer shell and form molecules.

What are the key properties of simple molecular substances?

They have low melting and boiling points due to weak intermolecular forces, do not conduct electricity, and are usually gases or liquids at room temperature.

What are polymers and how are they formed?

Polymers are large molecules made from many small repeating units (monomers) joined by covalent bonds in a chain.

What are giant covalent structures and what are their properties?

These are substances with a continuous network of covalently bonded atoms. They have very high melting points, are hard, and usually do not conduct electricity (except graphite).

What are the main allotropes of carbon and how do they differ?

The main allotropes are diamond, graphite, graphene, and fullerenes. Diamond is hard and doesn't conduct electricity. Graphite is soft and conducts electricity. Graphene is a single layer of graphite, very strong and conductive. Fullerenes are molecules shaped like spheres or tubes.

Why are covalent bonds strong?

Because the shared electrons are attracted to the nuclei of both atoms, holding them tightly together.

What are intermolecular forces and how do they affect molecular substances?

Intermolecular forces are weak attractions between molecules. They determine the melting and boiling points of simple molecular substances-stronger forces mean higher boiling points.

Why don't simple covalent substances conduct electricity?

They don't have free electrons or ions to carry a charge.

What are the typical properties of polymers?

Polymers are usually solid at room temperature, have relatively high melting points (compared to simple molecules), and are often flexible or strong depending on their structure.

What makes diamond so hard?

Each carbon atom is bonded to four others in a rigid 3D structure, making it extremely strong and hard.

Why can graphite conduct electricity?

Each carbon atom forms three bonds, leaving one free electron per atom that can move through the layers.

What is graphene and what are its uses?

Graphene is a single layer of carbon atoms arranged in a hexagonal lattice. It is extremely strong, light, and an excellent conductor-used in electronics and materials science.

What are fullerenes and what are they used for?

Molecules of carbon shaped like hollow balls or tubes (e.g., buckyballs, nanotubes). Used in drug delivery, lubricants, and nanotechnology.

Why do giant covalent structures have high melting points?

Because many strong covalent bonds must be broken for the structure to melt, which requires a lot of energy.

What's the main difference between simple molecular and giant covalent substances?

Simple molecules have weak forces between them and low melting points, while giant covalent structures have strong covalent bonds throughout and high melting points.