Both chlorine and bromine are used as disinfectants for drinking water, swimming pools, fresh wounds, spas, dishes, and surfaces. They kill bacteria and other potentially harmful microorganisms through a process known as sterilization.
Chlorine and bromine are also used in bleaching. Sodium hypochlorite, which is produced from chlorine, is the active ingredient of most fabric bleaches. Chlorine-derived bleaches are also used in the production of some paper products. Iodine is an essential mineral for the body. It is used in the thyroid gland but can also be found in breast tissue, salivary glands, and adrenal glands.
Without iodine, thyroid hormones cannot be produced, which leads to a condition called hypothyroidism. Without treatment, the thyroid gland will swell and produce a visible goiter. Children with hypothyroidism may develop mental retardation. In women, hypothyroidism can lead to infertility, miscarriages, and breast and ovarian cancer. Thyroid problems have been a common issue for many years, particularly in middle aged women; studies correlate this with the fact that iodine levels in the general population have significantly decreased in recent years.
Because of certain health problems, many people have been consuming less salt, which usually contains iodine. In drug discovery, the incorporation of halogen atoms into a lead drug candidate results in analogues that are usually more lipophilic and less water-soluble. Therefore, halogen atoms are used to improve penetration through lipid membranes and tissues. It follows that there is a tendency for some halogenated drugs to accumulate in adipose tissue.
Polyhalogenated compounds PHCs are of particular interest and importance because halogens are generally highly reactive and bioaccumulate in humans.
DDT dichlorodiphenyltrichloroethane is a polyhalogenated pesticide that was banned in the United States in because of the potential harmful effects on human health. In the second half of World War II, it was used to control malaria and typhus among civilians and troops. The US ban on DDT is cited by scientists as a major factor in the comeback of the bald eagle, the national bird of the United States, from near extinction. It is now banned in the United States because of its potential harmful effects on human health.
Key: chlorine atoms: green, carbon atoms: black, hydrogen atoms: white. PHCs are generally immiscible in organic solvents or water but miscible in some hydrocarbons, from which they are often derived. PHCs are used in a vast array of products and industries, such as:.
Privacy Policy. Skip to main content. Nonmetallic Elements. Search for:. Halogens Properties of the Halogens Halogens fluorine, chlorine, bromine, iodine, astatine are nonmetal elements that are highly electronegative and reactive. Learning Objectives Describe the physical and chemical properties of halogens. Down the group, atom size increases.
As a diatomic molecule, fluorine has the weakest bond due to repulsion between electrons of the small atoms. Due to increased strength of Van der Waals forces down the group, the boiling points of halogens increase. Therefore, the physical state of the elements down the group changes from gaseous fluorine to solid iodine. Due to their high effective nuclear charge, halogens are highly electronegative.
Therefore, they are highly reactive and can gain an electron through reaction with other elements. Halogens can be harmful or lethal to biological organisms in sufficient quantities. Key Terms electronegativity : The tendency of an atom to attract electrons to itself. They share similar chemical properties. Halogen Compounds Halogens are highly reactive and can form hydrogen halides, metal halides, organic halides, interhalogens, and polyhalogenated compounds.
Learning Objectives Discuss halogen compounds and their properties. Key Takeaways Key Points Hydrogen halides are binary compounds of halogens with hydrogen. They are strong hydrohalic acids when dissolved in water, with the exception of HF.
Halogens have the ability to form compounds with other halogens interhalogens. They are represented with the notation XY, in which the X and Y refer to two different halogens. Examples of this type of molecule include IBr and BrCl.
Properties of Halogens Elements such as fluorine, chlorine, bromine, iodine, and astatine belong to Group 17, the halogen group. Reaction with Water From a standard reduction potential table, it is determined that iodine and bromine cannot oxidize water to oxygen because they have smaller reduction potentials than oxygen.
Reaction with Hydrogen All the halogens react directly with hydrogen, forming covalent bonds and—at sufficient levels of purity—colorless gases at room temperature. Group 1: The Alkali Metals All the alkali metals react vigorously with halogens to produce salts, the most industrially important of which are NaCl and KCl.
Silicon Halides Silicon reacts with halogens to form compounds of the form SiX 4 , where X represents any common halogen. Metal Halides Lead and tin are metals in Group Halogen Oxoacids Compounds that are made up of both oxygen and hydrogen are considered to be oxygen acids, or oxoacids.
Group Other Halogens Interhalogens Halogens have the ability to form compounds with other halogens interhalogens. References Hill, Graham, and John Holman. Chemistry in context. Nelson Thornes, Atkins, Peter, and Loretta Jones. Chemical Principles. Freeman, Hessler, John. Essentials of Chemistry. New York: B. Name four chlorine oxoanions.
Which metal forms a dimer when reacted with halogen? HClO 2. HBrO 3. HIO 3. HClO 3. HBrO 4. Permitted use: Download. They are like nobility in the sense that they don't mix with the riffraff. They don't like to react with any other elements. Oh, ho, ho, ho! The noble gases, like neon and argon, pose a problem for chemists who prefer their elements to join forces and react with each other. You can run an electric current through them, excite their electrons and get pretty colors—which is how neon lights work—but the noble gases don't react.
THEO GRAY: Being an inert gas, being unwilling to mix with the other elements, react with them, this is a very clear-cut distinction that sets apart this particular column from all the others in the periodic table. As it turns out, protons may determine the identity of an element, but electrons rule its reactivity. And reactivity is a shell game. Imagine that these balls are electrons, and the target is an atom.
Electrons don't just pile on around the nucleus. As with skee-ball, where you land, relative to the center counts. The electrons take up positions in what can be thought of as concentric shells. The first shell maxes out at just two electrons, the next holds eight, then it goes up to eighteen. An atom with eight electrons in its outer shell makes one happy, satisfied atom.
They are called the halogens.
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