Problem 58 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following sets has the strongest tendency to form anions? (a) \(\mathrm{V}, \mathrm{Cr}, \mathrm{Mn}\) (b) \(\mathrm{N}, \mathrm{O}, \mathrm{F}\) (c) \(\mathrm{Ga}, \mathrm{In}, \mathrm{TI}\) (d) \(\mathrm{Na}, \mathrm{Mg}, \mathrm{Al}\)

Step-by-Step Solution

Answer

Group (b) \( N, O, F \) has the strongest tendency to form anions.

Step 1: Understanding Anion Formation

Anions are negatively charged ions formed when atoms gain electrons. Elements with high electronegativity and high electron affinity tend to form anions more readily.

Step 2: Analyzing Electronegativity in Group (a)

The elements V (Vanadium), Cr (Chromium), and Mn (Manganese) are transition metals. Transition metals generally have lower electronegativity compared to non-metals, thus they do not have a strong tendency to form anions.

Step 3: Analyzing Electronegativity in Group (b)

The elements N (Nitrogen), O (Oxygen), and F (Fluorine) are non-metals. They have high electronegativity values, with Fluorine being the most electronegative element. These elements, especially Fluorine, have a strong tendency to form anions.

Step 4: Analyzing Electronegativity in Group (c)

The elements Ga (Gallium), In (Indium), and Tl (Thallium) are post-transition metals. Compared to non-metals, these elements have lower electronegativity and electron affinities, which means they form anions less readily.

Step 5: Analyzing Electronegativity in Group (d)

The elements Na (Sodium), Mg (Magnesium), and Al (Aluminum) are in groups with a higher tendency to lose electrons and form cations, rather than gaining electrons to form anions.

Step 6: Conclusion

After analyzing the tendencies of each group, Group (b) with \( \mathrm{N}, \mathrm{O}, \mathrm{F} \) has the strongest tendency to form anions due to their high electronegativity and electron affinities, especially Fluorine which is the most electronegative element.

Key Concepts

Electronegativity

Electronegativity is a measure of an atom's ability to attract and hold onto electrons. Atoms with high electronegativity have a strong pull on electrons, making them more likely to gain electrons and form negative ions or anions. In the periodic table, electronegativity tends to increase across a period from left to right and decreases down a group.

Fluorine, for instance, is the most electronegative element, which explains why it readily forms anions. Non-metals typically have higher electronegativity values compared to metals.

• This is due to their nearly filled valence shells, which makes them more eager to gain electrons to achieve a stable electronic configuration.

In contrast, metals have lower electronegativity, favoring the loss of electrons to form cations instead.

Electron Affinity

Electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gaseous state, forming an anion. Atoms with a high electron affinity release more energy upon gaining an electron, indicating a higher tendency to form anions.

Non-metals, like oxygen and fluorine, generally exhibit high electron affinity values, meaning they are ready to accept electrons and form negatively charged ions.

• This makes them crucial players in various chemical reactions and processes.

In contrast, elements like alkali metals have lower electron affinities as they favor losing rather than gaining electrons.

Non-metals

Non-metals are elements typically found on the right side of the periodic table. They are characterized by their high electronegativity and electron affinity, making them ideal candidates for gaining electrons to form anions.

Common non-metals include nitrogen, oxygen, and fluorine, all of which have a strong tendency to pull electrons from other atoms.

• For instance, fluorine is so electronegative that it defines the scale of electronegativity itself.

Non-metals often have higher ionization energies and poorer conductivity compared to metals. This unique set of properties allows them to play a crucial role in numerous compounds and reactions, frequently acting as oxidizing agents.

Transition Metals

Transition metals are a group of elements found in the central block of the periodic table, specifically from groups 3 to 12. Unlike non-metals, transition metals typically have lower electronegativity and electron affinity. This means they are less inclined to gain electrons and form anions. Instead, they are more likely to lose electrons, forming cations.

The flexibility in oxidation states is a hallmark of transition metals, allowing them to participate in a wide variety of chemical reactions.

• This property also makes them essential in industrial applications, such as catalysis and alloy production.

While transition metals might not readily form anions, their ability to bond in complex structures contributes significantly to their utility in chemistry and material science.