Argon (Ar)

Chemical and Physical Properties of Argon

Argon is a noble gas. The noble gases are the 7 elements in Group 18 (VIII A) of the periodic table (The periodic table is a chart that shows how the chemical elements are related to each other). The noble gases are also called inert gases because Group 18 (VIII A) elements react with so little other elements. In fact, no compound of argon has never been produced.

An English chemist by name John William Strutt, most popularly known as Lord Rayleigh (1842-1919), chemist William Ramsay (1852-1916) discovered Argon in 1894. It was the first kind of noble gases to be isolated.
Rayleigh and Ramsay found argon by the fractional distillation of liquid air. Fractional distillation is the method of letting liquid air slowly warm up. As the air warms, various elements change from a liquid back to a gas. The portion of air that converts back to a gas at -185.86°C (-302.55°F) is argon.

SYMBOL

Ar

ATOMIC NUMBER

18

ATOMIC MASS

39.948

FAMILY

Group 18 (VIII A) Noble gas

PRONUNCIATION

AR-gon

Argon is used to produce an inert blanket for certain industrial operations. An inert blanket of gas prevents any chemicals in the operation from reacting with oxygen and other few substances present in the air. Argon is also used in creating "neon" lamps and in lasers.

Discovery and naming of Argon:

Argon was discovered in the year 1894. However, English scientist Henry Cavendish (1731-1810) had predicted the existence of argon 200 years earlier before the discovery of argon. When Cavendish tried to remove oxygen and nitrogen from the air, he found that a very small amount of gas remained. He guessed correctly that another element was in the air, but he was unable to identify what it was.

When Ramsay repeated Cavendish's experiments in the year 1890s, he, too, found a tiny amount of unidentified gas in the air. But Ramsay had an advantage over Cavendish: he was able to use spectroscopy, which did not exist in Cavendish's time. Spectroscopy is the process in which the light produced is analyzed by heating an element. 
The spectrum (plural: spectra) of an element that consists of a series of colored lines and is different for every element.

Ramsay examined the spectrum of the unidentified gas. He obtained a series of lines that did not belong to any other element. He was convinced that he had discovered a new element. Meanwhile, Rayleigh was doing the same work at almost the same time. He made his discovery around the same time Ramsay did. Both scientists decided to make their announcement together. The name argon is derived from the Greek word Argos, "the lazy one." The name is based on argon's disability to react with anything.

The discovery of argon raised a problem for chemists. Argon was the first noble gas to be discovered by the scientist. Where should this element go to the periodic table? At that time, the periodic table ended with Group 17 (VIIA) at the right. Ramsay suggested that the periodic table might have to be extended. Ramsay proposed adding a whole new group to the table. That group would be placed to the right of Group 17 (VIIA) in the periodic table.

Ramsay's suggestion was accepted, but it created another interesting new problem for chemists. If there was a very new group in the periodic table, where were the other elements that belonged in the group? Fortunately, chemists had a good idea of what these unknown elements might look like. All of the elements in a single group are very much similar to each other. Chemists started looking for more inactive gases. Within the next five years, they had found the remaining members of the group and added them: helium, krypton, neon, radon, and xenon.

Physical properties:

Argon is a colorless, odourless, tasteless noble gas. The noble gas Argon has a density of 1.784 grams per liter. When we compare the density of argon with the density of air, is about 1.29 grams per liter. Argon changes its state from a gas to a liquid at -185.86°C (-302.55°F). Then it changes its state from a liquid to a solid at -189.3°C (-308.7°F)

Chemical properties:

The noble gas Argon is chemically inactive. On rare circumstances, and under extreme conditions, it forms weak, compound-like structures.

Occurrence in nature:

The abundance of argon in the atmosphere is around 0.93 percent. Argon is also found in the Earth's crust to the extent of about 4 parts per million.

Extraction:

The noble-gas Argon can be produced from liquid air by fractional distillation. Argon can also be produced by heating nitrogen gas from the atmosphere with hot magnesium or calcium. The magnesium or calcium mixes with nitrogen to form a nitride:

A little argon always occurs as an impurity with nitrogen gas. It stays behinds because it does not react with magnesium or calcium.

Argon can also occur in wells with natural gas. When the natural gas is purified, some argon can be recovered as a by-product of the reaction.

Isotopes:

The 3 isotopes of argon exist naturally. These isotopes are argon-36, Argon-38, and argon-40. Isotopes form two or more from an element. The Isotopes vary from each other according to their mass number. The mass number is written to the right of the element name is the mass number. The mass number is represented by the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons defines the element, but the number of neutrons in the atom of any one element can vary. Each change is an isotope element.

A radioactive isotope is the one that breaks apart and gives off some form of radiation. Radioactive isotopes are produced when small particles are fired at atoms. These particles stick in the atoms and make them radioactive element.

No radioactive isotopes of argon have any practical purpose. One non-radioactive isotope can be used, however, to find the age of very old rocks. This method of dating and finding the age of the rocks is described in the potassium entry

Uses:


  • • The noble gas Argon is used in situations where materials need to be protected from oxygen or other gases. A good example is an incandescent lightbulb, that consists of a metal wire inside a clear glass bulb. An electric current has to pass through the wire, which causes it to get very hot and give off light.

  • • Oxygen will combine with the hot metal very easily; this reaction forms a compound of the metal and oxygen. This compound will not conduct an electric current very well, thereby this can cause the lightbulb to stop giving off light.

  • • Argon, nevertheless, is used to prevent this from happening. Because argon is inert, it will not react with the hot wire, leaving the metal hot for a long period of time. The lightbulb will stop giving off the light only when the metal breaks. Then this can no longer carry an electric current.

  • • Argon can also be used in welding. Welding is the process in which two metals are joined with each other. In most of these cases, the two metals are heated to very high temperatures. As they get hotter and hotter, they melt together.

  • • However, as the metal gets hot, they begin to react with oxygen. In this reaction, a compound component of metal and oxygen is formed. It becomes difficult to combine these two metals if they have formed compounds but introducing argon into the welding environment improves the bond of these.

  • • Argon can also be used in argon lasers and argon-dye lasers. A laser is a device that gives very bright light of a single color (frequency). An argon laser is used to treat skin related conditions. The laser shines a blue-green light on the affected area of the skin in the body. The energy from the laser is absorbed by haemoglobin (Blood) and converted to heat. (Hemoglobin is the protein pigment in red blood cells in our body). The blood vessels are damaged but then sealed, prompting them to decompose and be reabsorbed into the human's body. Unwanted growths of this are flattened and dark spots are Lightened, with only a small risk of scarring.

  • • An argon-dye laser is actually used in eye surgery. The color of light produced by the laser can be calibrated with high precision. It can be made to produce light ranging over the green-to-blue color range. Each tone of green or blue has a slightly different frequency. It can enter more or less deeply in the eye. The laser can be modified to treat a very specific part of the eye. The argon dye is used to treat tumours, damaged blood vessels, conditions including the retina, and other kinds of eye problems.

  • Compounds:

    No compound of the noble gas argon has ever been produced.

    Health effects:

    Argon is not known to have any positive or negative effects on the health of plants, animals, and humans.