18.11 Occurrence, Preparation, and Properties of Halogens
3 min read•june 25, 2024
, the Group 17 elements, are fascinating and versatile. From to , they occur naturally in various forms and are extracted using clever methods. Their unique properties make them indispensable in many industries.
show clear trends in physical and chemical properties as you move down the group. These elements and their compounds have diverse applications, from water treatment to pharmaceuticals. Their chemistry is rich with and interesting .
Occurrence and Preparation of Halogens
Occurrence and preparation of halogens
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- Halogens occur naturally in various forms and sources
- and sodium commonly found together in seawater and salt deposits as (, table salt)
- Fluorine primarily found in mineral (, calcium fluoride) and (, sodium aluminum fluoride)
- present in seawater, salt lakes, and underground brines as (, sodium bromide)
- Iodine found in trace amounts in seawater, concentrated in seaweed, and in deposits (, sodium nitrate)
- Commercial preparation methods involve extracting and isolating halogens from natural sources
- Chlorine gas and sodium hydroxide produced by of aqueous sodium chloride solution ()
- Liquid sodium and chlorine gas obtained through of molten sodium chloride at high temperatures
- Bromine prepared by oxidizing with chlorine gas, displacing the bromine
- Iodine extracted by reacting iodide salts with more reactive halogens like chlorine or bromine, which displace the iodine
- are commonly used in halogen preparation, where a more reactive halogen displaces a less reactive one from its compounds
Properties and Applications of Halogens
Properties of halogen elements
- Physical properties vary systematically down the group
- State at room temperature changes from gas to liquid to solid: (gas), (gas), (liquid), (solid)
- Color becomes darker and more intense: F2 (pale yellow), Cl2 (yellowish-green), Br2 (reddish-brown), I2 (violet)
- Melting and boiling points increase down the group due to increasing atomic mass and stronger intermolecular forces ()
- Chemical properties also show trends within the halogen family
- Reactivity decreases in the order F2 > Cl2 > Br2 > I2, with fluorine being the most reactive and iodine the least
- (ability to accept electrons) follows the same trend, decreasing down the group
- (attraction for electrons in a bond) decreases: F (4.0), Cl (3.0), Br (2.8), I (2.5)
- Reaction with water varies: F2 and Cl2 react vigorously to form (, ) and oxygen; Br2 and I2 have limited reaction
- Halogens react with metals to form ionic , with reactivity decreasing down the group
- Hydrogen (HF, HCl, , ) are formed by direct combination, with acid strength increasing down the group
- Halogens exist as in their elemental form
Applications of halogens and compounds
- Water treatment heavily relies on chlorine and chlorine compounds for disinfection and purification ()
- Plastics industry uses halogens in polymers like () and (, )
- Pharmaceuticals often incorporate fluorine or chlorine in drug molecules (/, )
- Agrochemicals sector employs chlorine and bromine compounds in pesticides and herbicides (, )
- Flame retardants commonly use bromine compounds to reduce flammability of materials ()
- , particularly iodine vapor, are used in high-intensity discharge lighting ()
- Photography traditionally relied on and in photographic films and papers
- Refrigerants historically used , now replaced by () due to concerns
- reactions are widely used in organic synthesis to introduce halogen atoms into molecules
Halogen Chemistry and Reactions
- Halogens are located in Group 17 of the
- are formed when halogens gain one electron, becoming negatively charged
- Redox reactions play a crucial role in halogen chemistry, involving electron transfer between species
- Interhalogen compounds are formed when two different halogens combine, exhibiting unique properties and reactivities
Key Terms to Review (66)
Amphiphilic: Amphiphilic molecules have both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts. These dual characteristics allow them to interact with both aqueous and non-aqueous environments.
Br2: Br2, or bromine, is a chemical element that belongs to the halogen group in the periodic table. It is a dense, reddish-brown liquid that is highly reactive and plays a crucial role in the context of the topics covered in Section 18.11: Occurrence, Preparation, and Properties of Halogens.
Brine: Brine is a highly concentrated saltwater solution, typically containing a high concentration of dissolved salts, particularly sodium chloride. It is a key component in the occurrence, preparation, and properties of halogens, which are a group of five elements in the periodic table that includes fluorine, chlorine, bromine, iodine, and astatine.
Brine plays a crucial role in the extraction and processing of halogens, as it serves as a source of these elements and provides the necessary conditions for their production and purification.
Bromide Salts: Bromide salts are a class of chemical compounds that contain the bromide ion (Br-) as the anion, combined with a cation such as sodium, potassium, or ammonium. These salts are important in the context of the occurrence, preparation, and properties of halogens, as bromine is one of the five naturally occurring halogens.
Bromine: Bromine is a dense, reddish-brown liquid element that is part of the halogen group on the periodic table. It is highly reactive and has a wide range of applications, particularly in the chemical industry and in the production of various compounds.
CaF2: Calcium fluoride (CaF2) is an inorganic compound consisting of calcium and fluorine. This compound forms a crystalline solid that exhibits unique properties, such as high melting point and low solubility in water, making it significant in various applications like optics and metallurgy. Its connection to the solid state of matter is highlighted by its crystalline structure, while its relationship with halogens stems from its formation through the reaction of calcium with fluorine.
Chile Saltpeter: Chile saltpeter, also known as sodium nitrate, is a naturally occurring mineral compound that has been an important source of nitrogen for agriculture and industrial applications. It is closely related to the topics of 18.11 Occurrence, Preparation, and Properties of Halogens in the context of chemistry.
Chlorination: Chlorination is the process of introducing chlorine or chlorine-containing compounds into a substance, typically water or other materials, for the purpose of disinfection, oxidation, or chemical modification. It is an important concept within the context of the occurrence, preparation, and properties of halogens.
Chlorine: Chlorine is a highly reactive, greenish-yellow gas that is one of the five halogens in the periodic table. It is an essential element in many chemical processes and compounds, with wide-ranging applications in various industries and everyday life.
Chlorofluorocarbons: Chlorofluorocarbons (CFCs) are synthetic chemical compounds composed of carbon, chlorine, and fluorine atoms. They were widely used in the past as refrigerants, propellants in aerosol cans, and in the manufacturing of various products due to their stability, non-flammability, and non-toxicity. However, CFCs have been found to be harmful to the environment, particularly to the ozone layer in the Earth's atmosphere.
Chlorofluorocarbons (CFCs): Chlorofluorocarbons (CFCs) are a group of synthetic chemical compounds composed of carbon, chlorine, and fluorine atoms. They were widely used in the past as refrigerants, propellants in aerosol cans, and in the manufacturing of various products due to their stability and non-flammable properties. However, CFCs have been found to be harmful to the environment, particularly the ozone layer in the Earth's atmosphere.
Chlorpromazine: Chlorpromazine is a phenothiazine derivative that was one of the first antipsychotic medications developed. It is primarily used to treat schizophrenia and other psychotic disorders, as well as to manage nausea and vomiting.
Chlorpyrifos: Chlorpyrifos is an organophosphate pesticide that was widely used in agriculture to control a variety of insect pests. It is relevant in the context of the occurrence, preparation, and properties of halogens as it is a halogenated organic compound containing chlorine atoms.
Cl2: Cl2 is the chemical formula for chlorine gas, a highly reactive and poisonous element that is part of the halogen group on the periodic table. Cl2 plays a significant role in various chemical processes and reactions, particularly in the context of redox chemistry, the occurrence and properties of phosphorus, and the occurrence, preparation, and properties of halogens.
Cryolite: Cryolite is a rare, naturally occurring mineral composed of sodium, aluminum, and fluorine. It has a unique chemical composition and plays a significant role in the extraction and processing of aluminum, as well as in the context of halogen occurrence and preparation.
Diatomic Molecules: Diatomic molecules are chemical compounds composed of two atoms of the same element, bonded together to form a stable structure. These molecules are commonly found among the nonmetal elements and play a crucial role in understanding the properties and behaviors of various substances.
Displacement Reactions: A displacement reaction is a type of chemical reaction where an element in a compound is replaced by a more reactive element, resulting in the formation of a new compound. This process is particularly relevant in the context of the occurrence, preparation, and properties of halogens.
Electrolysis: Electrolysis is a chemical process in which electrical energy is used to drive a non-spontaneous chemical reaction. It involves passing an electric current through an electrolyte, causing ions to move and resulting in the deposition of substances at the electrodes.
Electrolysis: Electrolysis is the process of using electric current to drive a non-spontaneous chemical reaction. It involves the decomposition of chemical compounds by passing an electric current through them, resulting in the separation of their constituent elements. This process is fundamental to various applications, including the production of metals, the treatment of water, and the recharging of batteries.
Electronegativity: Electronegativity is a measure of an atom's ability to attract and hold onto electrons within a chemical bond. It is a dimensionless quantity usually assigned values on the Pauling scale.
Electronegativity: Electronegativity is a measure of an atom's ability to attract shared electrons in a chemical bond. It is a fundamental property that influences the nature and strength of chemical bonds, as well as the physical and chemical properties of substances.
F2: F2, or fluorine gas, is the diatomic form of the halogen element fluorine. It is a highly reactive and corrosive gas that is an essential component in the understanding of the occurrence, preparation, and properties of the halogens.
Fluorine: Fluorine is the lightest and most reactive of the halogen group of elements. It is a highly corrosive, pale yellow gas that is the most electronegative element on the periodic table. Fluorine's unique properties and reactivity make it an important element in various chemical and industrial applications.
Fluorite: Fluorite is a naturally occurring mineral composed of calcium and fluorine with the chemical formula CaF2. It is known for its diverse and vibrant colors and is commonly found in geological deposits around the world. Fluorite is an important mineral in the context of the occurrence, preparation, and properties of halogens, as it is a natural source of the halogen element fluorine.
Fluoxetine: Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) commonly prescribed as an antidepressant for the treatment of major depressive disorder and other mental health conditions. It works by increasing the levels of serotonin in the brain, which helps improve mood and reduce symptoms of depression. Understanding fluoxetine requires knowledge of its chemical structure, its interactions with neurotransmitters, and its synthesis, which can involve halogenated compounds.
Halide Ions: Halide ions are the negatively charged species formed when the halogens (fluorine, chlorine, bromine, iodine, and astatine) gain an electron to achieve a stable octet configuration. These ions are crucial in the occurrence, preparation, and properties of the halogens, as they play a central role in various chemical reactions and applications.
Halides: Halides are compounds formed when halogens react with other elements, typically metals. They are often binary compounds where halogen atoms combine with less electronegative elements.
Halogen Lamps: Halogen lamps are a type of incandescent light bulb that uses a halogen gas to increase efficiency and longevity. The halogen gas reacts with the tungsten filament, allowing it to operate at higher temperatures, which produces a brighter light and extends the life of the bulb. This technology is directly related to the properties and occurrences of halogens, as well as their preparation in the manufacturing process.
Halogenation: Halogenation is a chemical reaction that involves the addition of halogens, such as fluorine, chlorine, bromine, or iodine, to a compound, typically an organic molecule. This process can modify the physical and chemical properties of the compound, often increasing its reactivity. Halogenation is crucial in various applications, including the synthesis of organic compounds and in the transformation of hydrocarbons.
Halogens: Halogens are a group of elements in Group 17 of the periodic table known for their high reactivity and tendency to form salts with metals. They include fluorine, chlorine, bromine, iodine, and astatine.
Halogens: Halogens are a group of five highly reactive nonmetallic elements in the periodic table, including fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). These elements are known for their strong tendency to form ionic bonds and their widespread use in various applications.
HBr: HBr, or hydrobromic acid, is a colorless, corrosive, and highly reactive compound composed of hydrogen (H) and bromine (Br). It is an important chemical species that plays a role in the molecular structure and polarity of compounds, as well as in the occurrence, preparation, and properties of halogens.
HCl: HCl, or hydrogen chloride, is a chemical compound consisting of one hydrogen atom and one chlorine atom. It is a colorless, corrosive gas that has a wide range of applications and plays a crucial role in various chemical processes and reactions.
HF: HF, or hydrogen fluoride, is a colorless, corrosive gas that is the compound formed by the reaction of hydrogen and fluorine. It is a key term in the context of both molecular structure and polarity, as well as the occurrence, preparation, and properties of halogens.
HFCs: HFCs, or hydrofluorocarbons, are a class of synthetic chemical compounds that consist of hydrogen, fluorine, and carbon atoms. They are primarily used as refrigerants, propellants, and in various industrial applications, often as replacements for ozone-depleting substances.
HI: HI, or hydrogen iodide, is a colorless, diatomic gas that is the simplest binary compound of hydrogen and iodine. It is an important chemical species that is relevant in the context of both molecular structure and polarity, as well as the occurrence, preparation, and properties of halogens.
Homonuclear diatomic molecules: Homonuclear diatomic molecules are molecules composed of two identical atoms bonded together. Examples include $\text{H}_2$, $\text{O}_2$, and $\text{N}_2$.
Hydrofluorocarbons: Hydrofluorocarbons (HFCs) are a class of synthetic chemical compounds that contain hydrogen, fluorine, and carbon atoms. They are primarily used as refrigerants, propellants, and in various industrial applications, often as replacements for ozone-depleting substances.
Hydrogen Bromide: Hydrogen bromide, also known as hydrobromic acid, is a colorless, corrosive gas that is an important compound in the context of the occurrence, preparation, and properties of halogens. It is formed by the direct combination of hydrogen and bromine, and it plays a crucial role in various chemical processes and applications.
Hydrohalic Acids: Hydrohalic acids are a group of strong, corrosive acids formed by the combination of hydrogen (H) and a halogen (F, Cl, Br, I). These acids are important in the study of the structure and general properties of nonmetals, as well as the occurrence, preparation, and properties of halogens.
I2: I2, or diatomic iodine, is a chemical compound that is a member of the halogen group of elements. It is a solid at room temperature and has a characteristic purple-black color and distinctive odor. I2 is an important element in the context of the topics covered in section 18.11 Occurrence, Preparation, and Properties of Halogens.
Interhalogen Compounds: Interhalogen compounds are a class of chemical compounds formed by the covalent bonding of two different halogen elements, such as fluorine, chlorine, bromine, or iodine. These compounds exhibit unique properties and play a significant role in the occurrence, preparation, and properties of halogens.
Interhalogens: Interhalogens are compounds formed between two different halogens. They are generally more reactive than diatomic halogen molecules.
Iodine: Iodine is a essential trace mineral that plays a vital role in various physiological processes, particularly in the regulation of thyroid function. It is a member of the halogen group of elements and is known for its distinctive violet-blue color and unique chemical properties.
Metal Halide Lamps: Metal halide lamps are a type of electric lamp that produces light by using an electric arc to vaporize a mixture of mercury and metal halide additives. These lamps are commonly used for commercial and industrial lighting applications due to their high efficiency and bright, white light output.
Metal Halides: Metal halides are chemical compounds formed when metals bond with halogens. These compounds are significant in understanding the behavior and properties of halogens, as well as their occurrence and preparation processes. Metal halides exhibit unique characteristics that are influenced by the metal's oxidation state and the specific halogen involved, making them an essential focus in the study of halogens and their compounds.
Methyl bromide: Methyl bromide is a colorless, odorless gas that is a halomethane, primarily used as a pesticide and fumigant. It is an organobromine compound with significant agricultural applications, particularly in soil treatment and pest control, linking it directly to the properties and reactions of halogens.
Na3AlF6: Na3AlF6, also known as sodium hexafluoroaluminate or cryolite, is a chemical compound that is an important mineral and has applications in the production of aluminum and as a flux in metallurgy. It is a complex fluoride salt that consists of sodium and aluminum ions.
NaBr: NaBr, or sodium bromide, is an ionic compound composed of the sodium (Na+) and bromide (Br-) ions. It is an important halogen compound that has various applications and properties related to ionic and molecular compounds, as well as the occurrence, preparation, and properties of halogens.
NaCl: NaCl, commonly known as sodium chloride, is a chemical compound that consists of one sodium atom (Na) and one chlorine atom (Cl) bonded together. It is an ionic compound that is essential for various biological and industrial processes, and it is the primary component of table salt.
NaNO3: NaNO3, also known as sodium nitrate, is a chemical compound that consists of one sodium atom (Na) and one nitrate group (NO3). It is an important compound that is relevant in the contexts of writing and balancing chemical equations as well as the occurrence, preparation, and properties of halogens.
Oxidizing Power: Oxidizing power refers to the ability of a substance to gain electrons during a chemical reaction, thereby causing the oxidation of another substance. In the context of halogens, this property is significant as it determines how readily these elements can participate in redox reactions, influencing their reactivity and behavior in various chemical processes.
Ozone Depletion: Ozone depletion refers to the gradual thinning of the ozone layer in the Earth's atmosphere, which is responsible for absorbing harmful ultraviolet (UV) radiation from the sun. This phenomenon is primarily caused by the release of certain human-made chemicals, particularly chlorofluorocarbons (CFCs) and other halogenated compounds, into the atmosphere.
Periodic Table: The periodic table is a tabular arrangement of chemical elements organized by their atomic number, electron configuration, and recurring chemical properties. It serves as a fundamental tool in chemistry, providing a systematic way to classify and understand the behavior of elements based on their position within the table.
Polybrominated Diphenyl Ethers: Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame retardant chemicals that have been widely used in a variety of consumer products, including electronics, furniture, and textiles, to improve their fire resistance. These compounds are of concern due to their potential to persist in the environment and bioaccumulate in living organisms, leading to potential health and environmental impacts.
Polytetrafluoroethylene: Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer that is known for its remarkable chemical and thermal stability, as well as its low coefficient of friction. It is a key material in the context of the occurrence, preparation, and properties of halogens discussed in Section 18.11.
Polyvinyl Chloride: Polyvinyl chloride (PVC) is a widely used synthetic plastic polymer that is produced by the polymerization of the monomer vinyl chloride. It is known for its versatility, durability, and wide range of applications, particularly in the context of the occurrence, preparation, and properties of halogens discussed in Chapter 18.11.
Prozac: Prozac is a brand name for the antidepressant medication fluoxetine, which is a selective serotonin reuptake inhibitor (SSRI). It is commonly used to treat depression, anxiety, and other mental health conditions by regulating the levels of serotonin, a neurotransmitter that plays a crucial role in mood, sleep, and other bodily functions.
PTFE: PTFE, or polytetrafluoroethylene, is a synthetic fluoropolymer that is known for its exceptional chemical and thermal resistance, as well as its low coefficient of friction. It is a key material in the context of the occurrence, preparation, and properties of halogens.
PVC: PVC, or polyvinyl chloride, is a widely used thermoplastic polymer that is known for its versatility, durability, and cost-effectiveness. It is a key material in the context of the occurrence, preparation, and properties of halogens, as it is derived from the halogen element chlorine.
Redox Reactions: Redox (reduction-oxidation) reactions are a fundamental type of chemical reaction where the transfer of electrons occurs between two or more reactants. In these reactions, one substance is oxidized (loses electrons) while another is reduced (gains electrons), maintaining the overall charge balance.
Silver Bromide: Silver bromide (AgBr) is a chemical compound composed of silver and bromine. It is a light-sensitive material that has been widely used in photographic film and plates, making it an important component in the development of early photography.
Silver Iodide: Silver iodide is a chemical compound composed of silver and iodine. It is a key term in the context of the occurrence, preparation, and properties of halogens, as it is a naturally occurring halide salt that has important applications in various fields.
Sodium Chloride: Sodium chloride, commonly known as table salt, is a chemical compound composed of one sodium (Na) atom and one chlorine (Cl) atom. It is an ionic compound that is essential for various physiological processes in living organisms and has numerous industrial and household applications.
Teflon: Teflon is a brand name for polytetrafluoroethylene (PTFE), a synthetic polymer known for its nonstick properties and high resistance to heat and chemicals. It is primarily derived from the halogen fluorine, making its production and properties closely linked to the characteristics of halogens, especially in how they interact with organic compounds.
Van der Waals: Van der Waals forces are a type of weak intermolecular attractive force that arises between neutral atoms or molecules. These forces play a crucial role in the occurrence, preparation, and properties of halogens, the group of highly reactive nonmetallic elements that include fluorine, chlorine, bromine, iodine, and astatine.