Question

Consider the following properties of the noble gases: 1\. They readily form compounds which are colourless 2\. They generally do not form ionic compounds. 3\. They have variable oxidation states in their compounds 4\. Generally do not form covalent compounds Select the correct properties. (a) 1 (b) 1,3 (c) 2,3 (d) \(1,2,3\)

Short answer

Option (d) 1, 2, 3 are correct properties of noble gases.

Step-by-step solution

Analyze Property 1

Noble gases are known to be chemically inert and rarely react with other elements. However, some noble gases can form compounds, particularly with fluorine and oxygen. When these compounds exist, they tend to be colourless gases, solids, or liquids at room temperature. Hence, Property 1 is correct.

Analyze Property 2

Noble gases have a complete valence shell, making them unlikely to form ions and thus ionic compounds. This is because they have little tendency to gain or lose electrons. As such, Property 2 is correct.

Analyze Property 3

While noble gases are typically non-reactive, some, especially the heavier ones, can form compounds with other elements and exhibit variable oxidation states, such as xenon forming compounds with oxidation states like +2, +4, +6, and +8. Therefore, Property 3 is correct.

Analyze Property 4

Noble gases generally do not form covalent compounds due to their full valence shells, which make them chemically stable and non-reactive. However, under certain conditions, they can form covalent compounds with highly electronegative elements like fluorine. Since this is an exception rather than the rule, Property 4 is generally correct but not always applicable.

Select the Correct Properties

From the analysis, Properties 1, 2, and 3 are correct regarding noble gases. Although they are exceptions for Property 4, it slightly deviates due to the rare formation of some covalent compounds. The correct answer is thus option (d) 1, 2, 3.

Key concepts

Chemical Inertness

Noble gases, found in group 18 of the periodic table, are best known for their chemical inertness. This means they do not readily react with other elements. The reason behind this lies in their electronic configuration. Noble gases possess a complete outer electron shell, giving them a stable structure. In simple terms, their shells are full, so they don't "want" to gain or lose electrons. This lack of tendency to participate in chemical reactions is why they are labeled as inert.

Despite their general non-reactivity, under special conditions, some noble gases can form compounds. These situations usually involve high pressure or the presence of very reactive substances like fluorine. Even then, any compounds formed are typically colorless, aligning with the statement that noble gas compounds are often colorless. This uniqueness does not negate their fundamental nature of being chemically inert.

Oxidation States

While noble gases are predominantly known for their lack of reactivity, their ability to exhibit variable oxidation states is indeed an interesting property. This is mostly observed in the heavier noble gases, such as xenon and krypton, which can form compounds with multiple oxidation states.

One noteworthy example is xenon, which can form compounds having oxidation states from +2 to +8. The reason behind these varying oxidation states is the involvement of d and f orbitals in chemical bonding with highly electronegative elements. So, while oxidation states in noble gas compounds are uncommon, they do occur due to complex bonded structures in certain special cases, such as xenon's interaction with elements like fluorine and oxygen.

Ionic and Covalent Compounds

Noble gases are highly unlikely to form ionic compounds. They have a complete outer shell of electrons, which means they neither easily gain nor lose electrons to form ions. Their stable electronic configuration makes ionic bonding, which involves the transfer of electrons, improbable.

Regarding covalent compounds, noble gases generally do not form them either, given their chemical stability. However, there are exceptions. With elements like fluorine, which are very electronegative, certain noble gases can form covalent bonds under specific conditions. For example, compounds like xenon hexafluoroplatinate are covalent but extremely rare. Generally, their stable and "happy" electron arrangement means noble gases don't seek out bonds, further emphasizing their reluctance to form both ionic and covalent compounds in normal conditions.