The Covalent Bond
A covalent bond occurs between non-metal atoms and forms a very strong bond in which electrons are shared. A covalent bond can occur between atoms of the same element or atoms of different elements. It results in a formation of molecules.
A single covalent bond is formed when two atoms share one pair of electrons. Each atom shares one electron in the bond.
If two pairs of electrons are shared, a
If three pairs of electrons are shared a
Simple covalent structures are molecules with relatively few atoms. There are strong forces between the atoms in the molecules, but there are weak forces between the molecules.
This means that simple molecules have low melting and boiling points and have no overall charge so they cant conduct electricity. They do not attract water molecules so they often do not dissolve in water.
At room temperature many substances exist as gases...
The most common elements of Group 7 are chlorine, bromine and iodine. They are diatomic molecules (molecules containing two atoms which are covalently bonded by pair of electrons) They cannot occur as single atoms
They can be solid, liquid, or gas at room temperature depending on the strength of the forces holding the molecules together.
Giant molecules- covalent strucures-
Giant covalent structures may have many atoms joined to each other covalently throughtout the whole molecule. This makes the properties veery different from those of simple covalently bonded molecules
Diamond is a giant, rigid, covalent structure (lattice) where each carbon atom forms four covalent bonds with other carbon atoms.The large number of covalent bonds results in high melting/boiling points.
Uses of carbon structures...
- no electrical resistance - superconductors for use in electricity
- diodes and transisters
- ion storage for batteries
- reinforcement for buildings
- industrial catalysts.
Chemical based therapy;
refers to any form of medication that is taken to alleviate symptons of an illness. It ranges from prescriptions to homepathic medicines.
medicines work by replacing substances that are deficient or missing in the body- some medicines can alter the activity of the cells, aswell as destroy infectious microorganisms or abnormal cells.
homepathic treatments- alter the activity of cells.
They use very diluted doses of compounds or drugs that if strong enough would cause symptons of the illness of a healthy person.
Homepathic medicine is tailored to the individual patients.
Buckminsterfullerenes (buckyball, carbon-60)- a form of carbon that has molecules made of 60 carbon atoms. The atoms fold around and join together to make a ball shape. The carbon atoms form shapes of pentagons and hexagons like a football.
Carbon nanotube-a form of carbon made from a single layer of graphite rolled up to make a tube.