Covalent Bonding Flashcards
Covalent Bonding
Non-metal elements usually just need one or two electrons to fill their outer shell.
Covalent bonds are formed by sharing electrons. The shared electrons join the atoms together. This is called covalent bond.
Covalent Molecular Substances
Most covalent substances exist as discrete molecules.
Discrete covalent molecules are called covalent molecular substances.
The covalent bonds within these molecules (intramolecular forces) are strong but the bonds between molecules(intermolecular forces) are weak and easy to break.
Properties of covalent bonding
Low Melting and Boiling Point - the forces that hold the molecules together (intermolecular forces) are weak.
Do not conduct electricity - there are no charged particles that can move through the substance.
For soft solids - the forces that hold the molecules together are weak.
Tend to be malleable instead of shattering - the forces between molecules are weak so molecules are easily moved.
Variable solubility - solubility depends on the forces between the molecules( Intermolecular forces).
Why do some covalent molecular substances form solids:
A few substances that contain discrete covalent molecules are solids at room temperature. Theses are molecular solids.
Properties of Molecular solid
1.Low melting and boiling points
2.Usually soft and brittle
3.Cannot conduct electricity.
The weak force of attraction between the molecules can be broken by a small amount of energy. This means that the molecular solids are soft and brittle and melt and boil at low temperatures.
Molecular solids are also unable to conduct electricity because there are no free moving electrons or ions to carry a charge.
Covalent Network Structures.
A large three dimensional network of covalently bonded atoms.
Covalent Network Substances
In these substances from covalent bonds with multiple neighboring atoms resulting in a continuous array of covalently bonded atoms.
The intermolecular forces in covalent network substances are effectively covalent bonds and so require a significant amount of energy to disrupt.
Covalent Network Properties
Very high melting point - The covalent bonds that hold the atoms together are strong. Alot of energy is required to disrupt the this continoues array of convalently bonded atoms.
Do not conduct electricity - there are no charged particles that can move through the structure.The electrons are held in fixed positions within an atoms shell.
Extremely Hard and Brittle - bonds are very strong between the atoms so, but an impact force disrupts positions of atoms and causes the network to shatter.
Insoluble in water and most solvents - no attraction between the atoms in the network and water molecules.
Allotropes
Allotropes are different forms of the same element
Properties of Diamond:
Diamond are very hard - hardest natural substance
Very high melting and boiling points - lots of energy required to break the covalent bonds.
Cannot conduct electricity - there are no free electrons or ions to carry a charge.
Properties of Graphite
Graphite is soft and slippery – layers can easily slide over each other because the weak forces of attraction are easily broken. This is why graphite is used as a lubricant.
Graphite conducts electricity – the only non-metal to do so. The free electron from each carbon means that each layer has delocalized electrons, which can carry charge.
Fullerenes
Fullerenes are allotropes which consist of carbon atoms bonded to form an enclosed or partially closed mesh.
Buckminsterfullerene is one type of fullerene. It contains 60 carbon atoms, each of which is bonded to three others by two single bonds and one double bond.
Carbon nanotubes are another type of fullerene. They are cylindrical carbon molecules. They have many potential applications, such as transporting drugs around the body and as components in electrical transistors.
