вторник, 17 октября 2023 г.

Fluorine

 Fluorine

The element fluorine

<---Oxygen       Neon--->
  • Symbol: F
  • Atomic Number: 9
  • Atomic Weight: 18.998
  • Classification: Halogen
  • Phase at Room Temperature: Gas
  • Density: 1.696 g/L @ 0°C
  • Melting Point: -219.62°C, -363.32°F
  • Boiling Point: -188.12°C, -306.62°F
  • Discovered by: Henri Moissan in 1886


Fluorine is the first element in the group of halogens which occupies the 17th column of the periodic table. Fluorine atoms have 9 electrons and 9 protons. It is a fairly rare element in the universe, but is the thirteenth most common element in the Earth's crust.

Characteristics and Properties

Fluorine's most notable characteristic is that it is the most reactive of all the elements. This makes it dangerous and difficult to handle. It will react with nearly every other element. It is also the most electronegative of the elements, meaning that it attracts electrons towards itself.

In standard conditions fluorine forms a gas made up of two fluorine atoms called a diatomic gas. It is pale greenish-yellow in color with a pungent odor.

Fluorine is toxic for humans and very corrosive. Many of the reactions with fluorine are sudden and explosive. Fluorine will burn all sorts of compounds and elements including water, copper, gold, and steel.

Where is fluorine found on Earth?

Because it is so reactive, fluorine does not occur as a free element in nature. It is readily found in minerals in the Earth's crust including fluorspar, fluorapatite, and cryolite. The main source of commercial fluorine is fluorspar (which is also called fluorite). The majority of the world's fluorspar is supplied by China and Mexico.

How is fluorine used today?

Fluorine is rarely used in its pure form, but many compounds of fluorine are used by industry.

One of the most popular applications of fluorine is for refrigerant gases. For many years Chlorofluorocarbons (CFCs) were used for freezers and air conditioners. Today they have been banned because they damage the ozone layer. Many of the replacement gases still contain fluorine, however.

Another application is fluoride. Fluoride is a reduced form of fluorine when bonded to another element. Fluoride is helpful in preventing tooth decay and is used in tap water and toothpaste.

Other applications that use fluorine include high temperature plastics such as Teflon, the smelting of iron and metal production, pharmaceuticals, etching glass, and in processing nuclear fuel.

How was it discovered?

Although other chemists had suspected the presence of an unknown element in the compound fluoric acid, it was French chemist Henri Moissan who first successfully isolated the element in 1886.

Where did fluorine get its name?

The name fluorine is derived from the mineral fluorite which comes from the Latin word "fluere" meaning "to flow." The name was suggested by English chemist Sir Humphry Davy.

Isotopes

Fluorine has one stable isotope, fluorine-19. It is the only form that fluorine occurs in naturally.

Interesting Facts about Fluorine
  • Hydrofluoric acid is extremely dangerous and can be fatal.
  • Henri Moissan was awarded the Nobel Prize in 1906 for his discovery.
  • It is found in the gemstone topaz.
  • CFCs were once used as propellant in aerosol spray cans.
  • The bond formed between carbon and fluorine to make fluorocarbons is the strongest bond in organic chemistry and is very stable.
  • Cesium is sometimes called fluorine's opposite element because it is the least electronegative element.

Chlorine

 Chlorine

The element chlorine

<---Sulfur       Argon--->
  • Symbol: Cl
  • Atomic Number: 17
  • Atomic Weight: 35.45
  • Classification: Halogen
  • Phase at Room Temperature: Gas
  • Density: 3.2 g/L @ 0°C
  • Melting Point: -101.5°C, -150.7°F
  • Boiling Point: -34.04°C, -29.27°F
  • Discovered by: Carl Wilhelm Scheele produced the gas in 1774, but it was Sir Humphry Davy who first called it an element and named it chlorine in 1810
Chlorine is the second element in the seventeenth column of the periodic table. It is classified as a member of the halogen group. It has 17 electrons and 17 protons with 7 valence electrons in the outer shell. It is about the twentieth most abundant element in the Earth's crust.

Characteristics and Properties

Under standard conditions chlorine is a gas that forms diatomic molecules. This means that two chlorine atoms join together to form Cl2. Chlorine gas is greenish yellow, has a very strong odor (it smells like bleach), and is poisonous to humans. High concentrations of chlorine gas can be fatal.

Chlorine is very reactive and, as a result, is not found in its free form in nature, but only in compounds with other elements. It will dissolve in water, but will also react with water as it dissolves. Chlorine will react with all the other elements except the noble gases.

Most common chlorine compounds are called chlorides, but it also forms compounds with oxygen called chlorine oxides.

Where is chlorine found on Earth?

Chlorine can be found in abundance in both the Earth's crust and in ocean water. In the ocean, chlorine is found as part of the compound sodium chloride (NaCl), also known as table salt. In the Earth's crust, the most common minerals containing chlorine include halite (NaCl), carnallite, and sylvite (KCl).

How is chlorine used today?

Chlorine is one of the most important chemicals used by industry. Tens of billions of pounds of chlorine are produced each year in the United States alone for use in industrial applications. It is used in making a variety of products including insecticides, pharmaceuticals, cleaning products, textiles, and plastics.

You have probably heard people mention that chlorine is used in pools. Chlorine is used in pools to keep it clean and safe by killing bacteria, germs, and algae. It is also used in drinking water to kill bacteria so we don't get sick when we drink it. Because it kills germs, chlorine is also used in disinfectants and is the basis for most bleaches.

Chlorine is needed for the survival of animal life in the form of table salt (NaCl). Our body's use it to help us digest food, move our muscles, and fight off germs.

How was it discovered?

Chlorine gas was first produced by Swedish chemist Carl Wilhelm Scheele in 1774. However, for many years scientists thought that the gas contained oxygen. It was English chemist Sir Humphry Davy who proved that it was a unique element in 1810. He also gave the element its name.

Where did chlorine get its name?

Chlorine gets its name from the Greek word "chloros", which means "yellow-green."

Isotopes

Chlorine has two stable isotopes: Cl-35 and Cl-37. Chlorine found in nature is a mixture of these two isotopes.

Interesting Facts about Chlorine
  • Chlorine gas was used by the Germans in WWI to poison the Allied soldiers.
  • Around 1.9% of the ocean's mass is composed of chlorine atoms.
  • It has a high density for a gas of 3.21 grams per liter (air is around 1.29 grams per liter).
  • Chlorine is used to make chlorofluorocarbons or CFCs. CFCs were once widely used in air conditioners and spray cans. Unfortunately, they contributed to destroying the ozone layer and have been mostly banned.
  • Most chlorine gas for industry is produced by using electrolysis on water that contains dissolved sodium chloride (salt water).

Iodine

 Iodine

  • Symbol: I
  • Atomic Number: 53
  • Atomic Weight: 126.904
  • Classification: Halogen
  • Phase at Room Temperature: Solid
  • Density: 4.933 grams per cm cubed
  • Melting Point: 113.7°C, 236.66°F
  • Boiling Point: 184.3°C, 363.7°F
  • Discovered by: Bernard Courtois in 1811
Iodine is the fourth element in the seventeenth column of the periodic table. It is classified as a halogen and a non-metal. Iodine atoms have 53 electrons and 53 protons with 7 valence electrons in the outer shell.

Characteristics and Properties

Under standard conditions iodine is a dark blue-black solid. Iodine crystals can sublimate directly from a solid to a gas. As a gas, iodine is a purple vapor.

Iodine is a fairly active element, but is somewhat less active than the other halogens above it in the periodic table which include bromine, chlorine, and fluorine. Iodine can form compounds with many elements. Some of its most common compounds are formed with sodium and potassium.

Pure iodine can be dangerous to handle causing the skin to burn and damage to the eyes.

Where is it found on Earth?

Iodine is fairly rare, but is found in both the Earth's crust and in ocean water. There is actually a higher concentration of iodine in the ocean than in the Earth's crust. Some ocean plants such as seaweed have a high concentration of iodine. It is also found in underground brines near oil and natural gas reserves.

How is iodine used today?

Iodine has a number of uses. It is used in sanitation systems and as an antiseptic to kill germs and bacteria. It is also used in its radioactive form to enable doctors to diagnose medical issues and diseases.

Other applications include animal feed, cloud seeding, dyes, and photography.

Iodine is also an essential element for life. It plays an important role in the thyroid gland that controls the body's growth rate. Too little iodine can cause a person to have stunted growth and slower cognitive development (less intelligent). To make sure that people get enough iodine, it is often added to salt in what is called iodized salt.

How was it discovered?

Iodine was first discovered and isolated by French chemist Bernard Courtois in 1811. Courtois stumbled across iodine when running experiments on seaweed. It was French chemist Gay-Lussac who first named iodine as a new element and suggested the name.

Where did iodine get its name?

Iodine gets its name from the Greek word "iodes" which means "violet."

Isotopes

Iodine has one stable isotope that occurs naturally, iodine-127.

Interesting Facts about Iodine
  • Many people get the iodine they need in their diets from eating seaweed.
  • It is the heaviest element that is essential for human life and health.
  • Foods rich in iodine include fish, diary products (milk, cheese, yogurt), some fruits and vegetables, and iodized salt.
  • Pregnant women need more iodine than the average person. They can get this through dietary supplements.
  • Too much iodine is harmful and can make a person very sick. Never take iodine unless instructed by a doctor.