Argon – Sources, Physical Properties, Chemical Properties and Uses, Practice Problems and FAQ

Meet Mr Sloth Bear! He is too lazy to even walk around for a while. In fact, he is the slowest terrestrial mammal on earth. It seems that all his energy and reactivity ‘Argon’!! 

If you get the intended pun here, you probably know about whom we are going to talk.

The chemical element argon has the atomic number 18 and the symbol Ar. It is a noble gas that belongs to group 18 of the periodic table. At 0.934 % Argon is the third-most abundant gas in the Earth's atmosphere. The most prevalent noble gas in the crust of the Earth, argon makes up 0.00015 % of the crust.

TABLE OF CONTENTS

• Argon - Introduction and Source
• Argon - Physical Properties
• Argon - Chemical Properties
• Argon - Production
• Argon - Uses
• Practice Problems
• Frequently Asked Questions - FAQ

Argon - Introduction and Sources

The first gas from the noble gas family to be created by scientists is argon. In 1894, Scottish chemist William Ramsay and English physicist Lord Rayleigh both recognised the existence of argon. The word "argon" is derived from the Greek "argos," which means "lazy" or "not active."

The noble gas family, which includes argon, accounts for 0.93% of Earth's atmosphere. The third most abundant gas in the environment is thought to be argon. Inert gases are typically understood to be non-flammable, cryogenic gases.

The isotope argon-40, which forms through the radioactive decay of potassium-40, is the most abundant isotope of Argon on earth.

Argon - Physical Properties

• Argon is a noble gas that has no flavour, colour, or odour.
• It does not change colour when it becomes liquid or solid, unlike certain other gases. 
• It is not poisonous or flammable.
• It is gaseous at STP.
• It forms face-centred cubic crystals (fcc).
• However, because argon is 38% denser than air, it can displace oxygenated air in enclosed places, which poses a risk of asphyxiation.
• Argon produces a stunning blue-violet glow when it is agitated.
• Argon has never caused environmental harm. This is because the gas does not include any dangerous substances that can cause ozone depletion and instead occurs naturally in the environment.
• Argon is a non-combustible gas. However, argon tanks may blow up if they are near the fire because the heat will cause the pressure within the tank to rise until it reaches its boiling point.

Argon - Chemical Properties

• When heated, argon gives out a blue-violet glow. Argon lasers have a distinctive blue-green glow to them.
• Argon is inert in nature and hence generally tends to remain in 0 oxidation state.
• The electronic configuration of Ar is 1s² 2s² 2p⁶ 3s² 3p⁶.
• Noble gas atoms are inert or non-reactive since they contain a full valence electron shell. Argon compounds are not easily formed.
• Although argon fluorohydride (HArF) has been seen at temperatures below 17 K, there are no stable compounds known at normal temperature and pressure. 
• With water, argon creates clathrates by trapping argon atoms inside water molecules. Ions like ArH⁺ and other ions as well as complexes in the excited state, including ArF, have been seen. 
• Although they have not yet been created, scientists, according to theoretical values, think stable argon compounds should exist.
• The radioactive disintegration of Potassium-40 into Argon-40 is the primary source of argon on Earth. The isotope Ar-40 makes up more than 99 per cent of the argon that exists on Earth.
• Argon-36, which is created when stars with masses about 11 times bigger than the Sun are in their silicon-burning phase, is the isotope of argon that is most prevalent in the universe (but not on earth!). In this stage, a silicon-32 nucleus receives an alpha particle (helium nucleus) addition, forming sulphur-34, which then receives an alpha particle addition to become argon-36. Calcium-40 is created when some argon-36 combines with an alpha particle. Argon is a very uncommon gas in the cosmos.
  

Argon - Production

By fractionally distilling liquid air in a cryogenic air separation unit, which separates liquid nitrogen (boils at 77.3 K) from argon (boils at 87.3 K) and liquid oxygen (boils at 90.2 K), argon is industrially extracted. The annual global production of argon is about 700,000 tonnes.

The most common isotope of argon^,40Ar , is created when ⁴⁰K, which has a half-life of years, decays either by electron capture or positron emission. It is used in potassium-argon dating to establish the age of rocks.

Argon - Uses

• Industrial fractional distillation of liquid air produces argon. 
• An argon atmosphere is utilised in graphite electric furnaces to keep the graphite from burning. Argon is primarily used as an inert shielding gas in welding and other high-temperature industrial operations where typically unreactive material becomes reactive.
• Along with other gas-discharge tubes, incandescent, fluorescent, and other lighting fixtures employ argon. A characteristic blue-green gas laser is produced by argon. Fluorescent glow starters also use argon.
• It can be found in glow tubes, lasers, plasma balls, lightbulbs, and rocket propellant.
• For welding, keeping delicate chemicals, and safeguarding materials, it serves as a protective gas.
• In aerosol cans, compressed argon is occasionally employed as a propellant.
• Groundwater and ice core samples can be utilised to determine their ages using argon-39 radioisotope dating.
• In cryosurgery, liquid argon is utilised to remove malignant tissue. Both laser and argon plasma beams are employed in medical procedures.
• To aid in the removal of dissolved nitrogen from the blood during decompression, such as after deep-sea diving, argon can be added to create a breathing mixture called Argox.
• In scientific investigations such as neutrino tests and dark matter studies, liquid argon is employed. Despite being a plentiful element, argon has no known biological functions.
• Argon plasma coagulation (APC) is an electrosurgical technique that coagulates tissue by using Argon discharges at atmospheric pressure. Because it is biochemically inert, has a low breakdown voltage, and is very inexpensive, Argon was chosen.
• Argon plasma coagulation utilises electricity to conduct Argon plasma as a medium to give a higher frequency current to clot the tissue. The non-contact characteristic allows fast coagulation with very little control and injury to the tissues.
• In electric lamps, Argon is utilised as the filling for lamps that are incandescent filament and also used as a discharge of neon tubes that are utilised in the making of advertising signs.
• Argon gas is widely utilised as a filing in fluorescent light bulbs so that oxygen is prevented from wearing the filament of the bulb that tends to get heated up at very high temperatures. 
• Argon is also utilised to organise makeshift inert atmospheres that need shielding from other gases for purposes such as welding and rising semiconductor crystals.

Practice Problems

Q1. The most abundant noble gas in Earth’s atmosphere is

A. He
B. Ar
C. Ne
D. Kr

Answer: Argon is the most abundant noble gas and the third most abundant gas in the Earth's atmosphere with a concentration of 0.935%. Argon is the most abundant noble gas in the Earth's crust, accounting for 0.00015 % of the crust. 

So, option B) is the correct answer.
Q2. The most abundant isotope of Argon present on Earth is

A.  Argon-40
B.  Argon-36
C.  Argon-38
D.  Argon-53

Answer: The most common isotope of argon,⁴⁰Ar , is created when ⁴⁰K, which has a half-life of years, decays either by electron capture or positron emission. Argon-40, has 22 neutrons and makes up 99.6035 % of natural argon content. 

So, option A) is the correct answer. 

Q3. The electronic configuration of argon is?
Answer: The electronic configuration of Ar which has the atomic number, Z= 18 is 1s² 2s² 2p⁶ 3s² 3p⁶

Q4. How is Argon useful in metallurgical process?
Answer: Argon provides an inert atmosphere, even at very high temperatures, this property is made to use in metallurgical processes. Argon is injected into the metal during the refining process in metallurgy to agitate the metal. Argon can occasionally be utilised as a carrier gas for additions. Argon is fed into the elevating snorkel during the vacuum degassing procedure to aid metal circulation and degassing.

Frequently Asked Questions - FAQ

Question 1. How come argon is purple?
Answer: There are 18 protons and 18 electrons in an argon atom. Its outer shell contains eight electrons. Under typical circumstances, argon is a colourless and odourless gas. A blue-violet light is produced when argon is ignited by a high-voltage electric field.

Question 2. What occurs when you breathe in argon gas?
Answer: Because it is inert, this gas falls under the category of a fundamental asphyxiant. When inhaled, excessive amounts might result in faintness, nausea, vomiting, unconsciousness, and even death. If self-rescue is not possible, mistakes in judgement, confusion, or loss of consciousness can all result in death.

Question 3. What are the other elements present in argon’s group?
Answer: Group 18 is the group number of Argon, also called either noble or inert gases. The noble gases or inert gases in Group 18 of the periodic table include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). The name refers to some elements' virtually complete lack of reactivity with other elements or compounds.

Question 4. Is argon used in medicine?
Answer: In the medical industry, argon has also been employed as a surgical tool. A non-contact procedure called argon plasma coagulation (APC) employs high-frequency argon plasma stimulation to cauterise surrounding tissues and coagulate bleeding at surgical sites.

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