Covalent bonding (C2) Flashcards
What is a covalent bond?
When electrons are shared between non-metal atoms. The number of electrons depends on how many extra electrons an atom needs to make a full outer shell
What is a Single bond?
Each atom shares one pair of electrons
What is a Double bond?
Each atom shares two pairs of electrons
What are the three states of matter?
Solid, Liquid, and Gas
What is the boiling point?
The amount of energy required to turn a liquid into a gas
What determines the boiling point and melting point?
The forces between the particles, the higher the melting or boiling point of the substance, the stronger the forces are and vice versa
What is a Giant covalent bond and give an example?
Many billions of atoms, each one with a strong covalent bond to a number of others. One example is diamond
What are Small molecules and give an example?
Each molecule contains only a few atoms with strong covalent bonds between these atoms. Different molecules are held together by weak Intermolecular forces. For example, Water
What are Large molecules and give an example?
Many repeating units joined by covalent bonds to form a chain, the small section is bonded to many identical sections to the left and right.
Separate chains are held together by intermolecular forces that are stronger than in small molecules
One example is a Polymer
What are the properties of Giant covalent molecules?
High melting point and boiling points because the strong covalent bonds between the atoms must be broken down to melt or boil the substances.
Solid at room temperature
What are the properties of Small molecules?
Low melting and boiling points because only the intermolecular forces need to be overcome to melt or boil the substances, not the bonds between the atoms.
This does not require a lot of energy as the intermolecular forces are weak
Normally gaseous or liquid at room temperature
What are the properties of large molecules?
Melting and boiling points are low compared to giant covalent substances but higher than for small molecules
Large molecules have stronger intermolecular forces then small molecules, which require more energy to overcome.
Normally solid at room temperature
What is graphite?
A large covalent structure
What is the structure of Graphite?
Made only of carbon - each carbon atom bonds to three others, and forms hexagonal rings in layers. Each carbon atom has one spare electron, which is delocalised and therefore free to move around the structure
What is the Hardness of Graphite?
The layers can slide over each other because they are not covalently bonded. Graphite is therefore softer than diamond, even though both are made only of carbon, as each atom in diamond has four strong covalent bonds
What is the conductivity of Graphite?
The delocalized electrons are free to move through graphite, so can carry charges and allow electrical current to flow. Graphite is therefore a conductor of electricity.
What is Graphene?
Graphene consists of only a single layer of graphite. Its strong covalent bonds make it a strong material that can also conduct electricity. It could be used in composites and high tech electronics
What are Fullerenes?
Fullerenes are hollow cages of carbon atoms bonded together in one molecule. They can be arranged as a sphere or tube called a nanotube. The molecules are held together by weak intermolecular forces, so can slide over each other. They also conduct electricity
What was the first fullerene to be discovered and how many carbon atoms did it have?
Buckminsterfullerene was the first, and had 60 carbon atoms.
How can Fullerenes be used?
Lubricants and drug delivery
What are nanotubes and what are their properties?
The carbon atoms in nanotubes are arranged in cylindrical cubes. Their high tensile strength (difficult to break when pulled) makes them useful in electronics
