Group 18 Elements – Characteristics of Noble Gases

The group’s members have eight electrons in their outermost orbit (except helium which has two electrons). As a result, they have a stable configuration. Group 18 elements are gases that are chemically unreactive, meaning they do not form many compounds. Be a result, the elements are referred to as inert gases. Noble gas elements, like the other group elements, display trends in their physical and chemical properties.  The noble gas family’s general configuration is ns² np⁶ (except helium which has 1s²).

When the group’s members were found and named, they were assumed to be extremely rare as well as chemically inert, and hence were dubbed the rare or inert gases. However, it is now recognised that several of these elements are relatively abundant on Earth and across the cosmos, thus the term rare is deceptive. Similarly, the term inert has the disadvantage of connoting chemical passivity, implying that compounds of Group 18 cannot be produced. The term noble has long been used in chemistry and alchemy to describe the resistance of metals such as gold and platinum to undergo a chemical reaction.

Noble (Inert) Gases or Group 18 Elements

Noble or inert gases are elements in Group 18. They are named inert because they do not participate in any chemical reaction, hence they are chemically inert.

Helium, Neon, Argon, Krypton, Xenon, and Radon are all non-metallic elements of group 18.

In the periodic table, the zero group holds an intermediate position between the strong electronegative elements of the VIIA and strong electropositive elements of the IA groups, acting as a bridge. The noble gases are found in group 18 of the periodic table, which is located on the far right of the table. The 18th group members all have 8 electrons in their outermost shell.

Trends of Noble Gases

• Noble gas electronic configuration: Members of group 18 have eight valence electrons, which means they have eight electrons in their outermost orbit (except helium). As a result, they have a consistent octet configuration. Helium, on the other hand, has a duplet structure. The noble gas family’s general configuration is ns² np⁶ (except helium which has 1s²).
• Noble gas atomic radii: Members of group 18 have extremely small atomic radii. The atomic radii of noble gases grow down the group as the atomic number increases due to the addition of additional shells.
• Noble gas ionisation enthalpy: Noble gases have eight valence electrons, which means they have eight electrons in their outermost orbit (except helium). As a result, they have a stable octet or duplet configuration. As a result, the elements of group 18 have extremely high ionisation enthalpies. Because of the increase in atomic size, the ionisation enthalpy of noble gases drops along with the group.

Properties of Noble Gases

• Except for helium, all gases have the ns², np⁶ arrangement. Except for helium, the differentiating electron reaches the p-subshell, and hence all of these atoms are p-block elements.
• Except for helium, which has a 1s² structure and a totally filled 1st shell, all noble gases have an outermost shell with a complete octet.
• Because of their totally filled outer shell or stable structure, these elements, also known as noble gases, have no tendency to lose or gain electrons and so do not participate in chemical processes under normal conditions.
• All of these group 18 elements are gases at normal temperature and pressure conditions. Rn and Og are radioactive noble gases, and the rest are present in trace amounts in the atmosphere.
• Because of their insignificant presence in the atmosphere, these gases were given the label rare gases.
• Because of their insignificant presence in the atmosphere, these gases were given the label rare gases.
• Because they do not participate in any chemical reactions, they have been given the name inert gases.
• However, in addition to these noble gases, a number of xenon compounds and two Krypton fluorides were created.
• They are all monoatomic gases.

Physical Characteristics of Noble Gases

1. These gases have no colour, taste, or odour.
2. The Van der Waals forces between these elements’ particles are weak, but they become stronger as we progress down the group. This is due to an increase in the polarising capacity of the molecules.
3. Because of their stable nature, these are monoatomic gases in their free state.
4. Noble gases have low boiling and melting points. The low melting and boiling points of these gases are due to their weak Van der Waals force. These, however, rise as we progress along with the group.
5. At extremely low temperatures, certain elements can be condensed. The ease of liquefaction rises down the group as the atom size increases.
6. These are only marginally soluble in water. As we move down the group, solubility increases.
7. The noble gases have the biggest atomic radii in their respective eras.
8. The ionisation enthalpies of these noble gases are the highest in their respective periods because the electronic configuration is stable.

Chemical Characteristics of Noble Gases

This octet of electrons was assumed to be the most stable arrangement for the outermost shell of an atom in a chemical bonding theory established in 1916 by American chemist Gilbert N. Lewis and German scientist Walther Kossel. Although only noble-gas atoms had this arrangement, it was the state toward which all other element atoms tended in their chemical bonding. 

Certain elements satisfied this tendency by obtaining or losing electrons outright, resulting in the formation of ions; other elements shared electrons, generating stable combinations connected together by covalent bonds. The proportions in which atoms of elements bonded to create ionic or covalent compounds (their “valences”) were thus governed by the behaviour of their outermost electrons, which were dubbed “valence electrons” for this reason. This hypothesis described the chemical bonding of the reactive elements, as well as the relative inactivity of the noble gases, which came to be considered as their defining chemical property.

Sample Questions

Question 1: Group 18 Elements are not reactive? Why?

Answer:

The noble or inert gases are the group 18 elements. As the name implies, these are inert because they are chemically inert or non-reactive. Because of their totally filled outer shell, they have a stable electrical structure, which means they have no inclination to lose or gain electrons. Because these atoms have entire valence electron shells, the noble gases are exceedingly stable. These are highly unresponsive. Under typical conditions, they do not react or participate in any chemical reactions; nevertheless, there are some exceptions.

Question 2: Name the noble gases.

Answer:

Helium, argon, xenon, radon, neon, and krypton are examples of noble gases.

Question 3: How is the reactivity of noble gases under ordinary conditions?

Answer:

Under normal conditions, noble gases have no tendency to absorb or lose electrons. This is the only reason they are inert and do not participate in chemical reactions. Modern researchers have discovered that under certain conditions, noble gases can be induced to participate in a chemical reaction.

Question 4: What are noble gases why are they also called inert gases?

Answer:

Noble gases have no tendency to absorb or lose electrons under normal conditions. The only reason they are inert and do not participate in chemical reactions is because of this. Noble gases can be made to participate in a chemical process under particular conditions, according to modern researchers.

Question 5: Give reason why helium does not react with other elements.

Answer:

Helium has two electrons in its last orbital. It has a consistent electronic configuration. As a result, helium does not react with other elements.