As a group, halogens exhibit highly variable physical properties. Halogens range from solid (I2) to liquid (Br2) to gaseous (F2 and Cl2) at room temperature. The chemical properties are more uniform. The halogens have very high electronegativities.Fluorine has the highest electronegativity of all elements.alogens range from solid (I2) to liquid (Br2) to gaseous (F2 and Cl2) at room temperature. The chemical properties are more uniform. The halogens have very high electronegativities. Fluorine has the highest electronegativity of all elements.
A gene can exist in many different forms, calledalleles. For example, letâs say that there is one gene which determines the color of your hair. That one gene may have many forms, or alleles: black hair, brown hair, auburn hair, red hair, blond hair, etc. You inherit one allele for each gene from your mother and one from your father. Each of the two alleles you inherit for a gene each may be strong (dominant) or weak (recessive).
The brown gene alleles regulate the amount of melanins which are synthesized (eumelanin an pheomelanin are two common melanins). Generally, if more eumelanin is present, the color of the hair is darker; if less eumelanin is present, the hair is lighter. Pheomelanin colors hair orange and yellow. Everybody has some of both pigments. Hair color is a function of the relative amounts of these two pigments. The amounts of eumelanin pigments determine the varying darkness ranging from Ebony (BRN 1, dark black) to very light brown (BRN 19, sandy blonde).