Vision (Definition) Vision is a feature of a person's brain that allows him to see. He must have normal eyes, optic nerves (that stretch from the eyes to the back of his brain), and visual cortex (the vision center in the brain), in order to see properly. An ophthalmologist is a doctor specializing in vision. ...Read more.
The halogens or halogen elements (/ËhÃ¦lÉdÊÉn, ËheÉª-, -loÊ-, -ËdÊÉn/) are a group in the periodic table consisting of five chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). The artificially created element 117 (ununseptium) may also be a halogen.
For more information, see Halomethane. Haloalkane or alkyl halides are the compounds which have the general formula â³RXâ³ where R is an alkyl or substituted alkyl group and X is a halogen (F, Cl, Br, I). Haloalkanes have been known for centuries.Chloroethane was produced synthetically in the 15th century.or more information, see Halomethane. Haloalkane or alkyl halides are the compounds which have the general formula â³RXâ³ where R is an alkyl or substituted alkyl group and X is a halogen (F, Cl, Br, I). Haloalkanes have been known for centuries.