What are Noble Gases: Configuration Physical and Chemical Properties

The noble gases are the chemical elements that are present in group 18 of the periodic table. These elements are the most stable due to having the maximum number of valence electrons that their outer shell can hold. As they are already stable, they rarely react with other elements. Let’s know more about the topic, its properties along with few important questions. 

What are Noble Gases?

Noble gases are the elements present in group-18 of the modern periodic table. Their valence shell configuration is full, due to which they are chemically inert. They are also known as inert gases and aerogens. Group-18 belongs to the p-block in the modern periodic table.

They have very low chemical reactivity because of their stable electronic configuration. Because of this, they do not form molecules and are found as monoatomic gases. At normal room temperature and pressure, they are in a gaseous state.

Elements of group-18: Helium, Neon, Argon, Krypton, Xenon, Radon

General electronic configuration: [inert gas] ns²np6 (exception He: 1s²)

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Properties of Noble Gases

• Noble gases are found in the monoatomic form at room temperature and pressure.
• The atomic radius increases with atomic number as we go down in the group.
• These elements have low melting and boiling points.
• They do not possess any taste, color, or odor.
• They are sparingly soluble in water.
• Due to their stable electronic configuration, they are mostly chemically unreactive.

Properties of Helium

Of all the substances, Helium is found to have the lowest boiling point. It is a light and non-inflammable gas and is used in balloons for meteorological purposes. It is also used for experimental purposes, in nuclear reactors, and for clinical purposes. In small concentrations, helium is non-toxic. It is also the lightest noble gas.

Moreover, Helium is an s-block element that corresponds to period 1 and group 18 of the modern periodic table. The electron configuration of helium is 1s2 which is why this element has a total of 2 electrons in its valence shell. The density of this element corresponds to 1.7186 grams per litre under standard conditions for temperature and pressure. But in its liquid state, the density becomes approximately equal to 0.145 grams per cube centimetre.

Atomic Symbol: He

Atomic Number: 2

Electronic Configuration: 1s²

Period: 1

Valence electrons: 2

Properties of Neon

Neon is the second-lightest noble gas. It is used in light bulbs and making advertising signs. Although under standard conditions for temperature and pressure (STP), it is colourless under normal conditions, it turns reddish-orange in a vacuum discharge tube. It is also used as a cryogenic refrigerant. This gas does not possess any characteristic odor. 

Moreover, neon is the second-lightest noble gas after helium. The boiling point of neon is 27.104 Kelvin (or -246.046 degrees Celsius). At STP, the density of this gas is approximately equal to 0.9 grams per litre. However, in its liquid state i.e, at a temperature equal to its boiling point, the density of neon is equal to 1.207 grams per cubic centimeter.

Atomic Symbol: Ne

Atomic Number: 10

Electronic Configuration: [He] 2s²2p⁶

Period: 2

Valence electrons: 8

Properties of Argon

After nitrogen and oxygen, argon is the third most abundant gas in the atmosphere with a concentration of 0.93%. Argon is often used to create an inert atmosphere in industrial processes. One such use is for the production of titanium and other reactive elements.

Under standard conditions for temperature and pressure, argon exists as a colorless gas that displays a violet or lilac-colored glow when it is placed in an electric field.

Moreover, Argon is a p-block element that is equal to group 18 and period 3 of the modern periodic table. The melting point of argon is 83.81 Kelvin while its boiling point corresponds to 87.302 Kelvin and under the STP, the density of argon is approximately equal to 1.784 grams per litre.

Atomic Symbol: Ar

Atomic Number: 18

Electronic Configuration: [Ne] 3s²3p⁶

Period: 3

Valence electrons: 8

Properties of Krypton

Krypton is among the rarest gases found on Earth. It is used in fluorescent lights. One of its isotopes, 85Kr, is used in the medical field. It is not completely unreactive like other noble gases and reacts with chlorine gas and the gas is also known to be tasteless.

The melting point of this element corresponds to 115.78 Kelvin (approximately) whereas the boiling point of this element corresponds to 119.3 Kelvin. Under the standard temperature and pressure, the density of this element is roughly equal to 3.75 grams per litre.

Atomic Symbol: Kr

Atomic Number: 36

Electronic Configuration: [Ar] 3d¹⁰4s²4p⁶

Period: 4

Valence electrons: 8

Properties of Xenon

Xenon is a heavy and rare noble gas. It is 4.5 times heavier than air. In the medical field, it is used as an anesthetic agent. It has applications in photography where it is used in high-speed flashbulbs. Unlike other inert gases, Xenon is known to form some chemical compounds.

Under standard conditions, this element exists as a monoatomic gas that is colorless as well as odorless. The melting point of xenon corresponds to 161.4 Kelvin whereas the boiling point of this element corresponds to 165.05 Kelvin. Under the standard temperature and pressure, the density of xenon is approximately equal to 5.89 grams per litre.

Atomic Symbol: Xe

Atomic Number: 54

Electronic Configuration: [Kr] 4d¹⁰5s²5p⁶

Period: 5

Valence electrons: 8

Properties of Radon

Radon is a radioactive gas and is not found directly in the atmosphere. It is one of the rarest elements of the group. 222Rn is the most stable isotope of radon and has a half-life of 3.8 days. One of the prominent uses of radon is in cancer therapy.

Under standard conditions of temperature and pressure, radon, like most other noble gases, is a colorless and odorless gas and does not have any characteristic taste. The melting and boiling points of radon correspond to 202 Kelvin and 211.5 Kelvin respectively.

Atomic Symbol: Rn

Atomic Number: 86

Electronic Configuration: [Xe] 4f¹⁴5d¹⁰6s²6p⁶

Period: 6

Valence electrons: 8

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Things to Remember

• Group-18 elements are mostly chemically unreactive because of their stable electronic configuration and thus are known as noble gases or inert gases.
• Their general electronic configuration is of the type [inert gas] ns2np6, except for Helium, whose configuration is 1s2.
• Under normal conditions of room temperature and pressure, group-18 elements are found in gaseous form. They are found in monoatomic forms and are colourless, odorless, and tasteless.
• Helium has the lowest boiling point of all substances.
• Neon turns reddish-orange in a vacuum discharge tube but is otherwise colorless under normal conditions.
• Argon has the third-highest concentration of all gases on earth.
• Xenon was the first inert gas found to react to form chemical compounds.
• Radon is radioactive in nature and is used in cancer therapy.