Question

The electronic configuration of four elements are (1) \([\mathrm{Xe}] 6 \mathrm{~s}^{1}\) (2) \([\mathrm{Xe}] 4 \mathrm{f}^{14} 5 \mathrm{~d}^{1} 6 \mathrm{~s}^{2}\) (3) \([\mathrm{Ar}] 4 \mathrm{~s}^{2} 4 \mathrm{p}^{5}\) (4) \([\mathrm{Ar}] 3 \mathrm{~d}^{7} 4 \mathrm{~s}^{2}\) Which one of the following statements about these elements is not correct? (a) (1) is a strong reducing agent (b) (2) is a d block element (c) (3) has high electron affinity (d) (4) shows variable oxidation state

Short answer

None of the statements are incorrect; all are correct.

Step-by-step solution

Analyze the first element

Element (1) has the electronic configuration \([\mathrm{Xe}] 6 \mathrm{~s}^{1}\), which indicates that it is in Group 1 of the periodic table. Elements in this group, such as cesium, are known as alkali metals and are good reducing agents. Therefore, statement (a) is correct.

Analyze the second element

Element (2) has the electronic configuration \([\mathrm{Xe}] 4 \mathrm{f}^{14} 5 \mathrm{~d}^{1} 6 \mathrm{~s}^{2}\). This indicates it is a lanthanide, specifically lanthanum. Lanthanides are part of the f-block, but lanthanum is classified as a d-block element. Therefore, statement (b) is correct.

Analyze the third element

Element (3) has the electronic configuration \([\mathrm{Ar}] 4 \mathrm{~s}^{2} 4 \mathrm{p}^{5}\), identifying it as a halogen, specifically bromine. Halogens are known for their high electron affinity as they are one electron short of completing their p-orbital to achieve a stable noble gas configuration. Therefore, statement (c) is correct.

Analyze the fourth element

Element (4) has the electronic configuration \([\mathrm{Ar}] 3 \mathrm{~d}^{7} 4 \mathrm{~s}^{2}\), identifying it as a transition metal, specifically cobalt. Transition metals are characterized by their ability to exhibit a variety of oxidation states due to their d electrons. Therefore, statement (d) is correct.

Conclusion

All statements provided are consistent with the properties of the elements based on their electronic configurations. None of the statements are incorrect, suggesting an error in the question or misunderstanding of its intent. It appears that all statements are indeed correct.

Key concepts

Reducing Agent

In chemistry, a reducing agent, or reductant, is a substance that donates electrons to another species. This process is known as reduction.
Reducing agents are often associated with electropositive metals. They have a high tendency to lose electrons to achieve a more stable electronic configuration.

The first element in the exercise, with the configuration element (1) \([\mathrm{Xe}] 6 \,\mathrm{s}^{1}\)belongs to Group 1 of the periodic table.
This group includes alkali metals like cesium, which are renowned for their role as effective reducing agents.
The ease with which these metals can donate their outermost electron accounts for their reactivity.

• Alkali metals have a single electron in their outermost shell.
• This makes them excellent at donating electrons.
• After losing an electron, they achieve a stable noble gas electron configuration.

Understanding the role of reducing agents is crucial for reactions involving electron transfer, especially in redox reactions.

d Block Elements

The d block elements, also known as transition metals,are characterized by having d electrons in their penultimate energy level. This category of elements is found in the center of the periodic table, covering groups 3 through 12.

Element (2) with the configuration \([\mathrm{Xe}] 4 \,\mathrm{f}^{14} 5 \,\mathrm{d}^{1} 6 \,\mathrm{s}^{2}\)is identified as lanthanum.
While lanthanides generally belong to the f-block, lanthanum is considered a part of the d-block because it includes electrons in the d orbital.

• d block elements are well known for their metallic properties.
• They often have high melting and boiling points.
• Most exhibit variable oxidation states, often forming colored compounds.

This classification underpins a fundamental understanding of the chemical behavior and reactivity of metals in this part of the periodic table.

Electron Affinity

Electron affinity is the measure of an atom's tendency to accept an electron. This property is significant for the elements that are near reaching a stable octet configuration, such as the halogens.
Element (3) with the electronic configuration \([\mathrm{Ar}] 4 \,\mathrm{s}^{2} 4 \,\mathrm{p}^{5}\)is a halogen, specifically bromine.
Halogens are just one electron short of completing their p-orbitals, leading them to have high electron affinities.

Some notable traits of electron affinity include:

• It is typically exothermic for halogens, meaning energy is released when an electron is added.
• Halogens have high electron affinities due to their strong desire to achieve noble gas configuration.
• Electron affinity can vary significantly across a period in the periodic table.

Grasping the concept of electron affinity helps explain why certain elements are highly reactive, especially toward gaining electrons.

Oxidation State

The oxidation state, often synonymous with oxidation number, indicates the degree of oxidation of an atom in a chemical compound.
It is a theoretical charge that an atom would have if all bonds were entirely ionic. Element (4) with the electronic configuration \([\mathrm{Ar}] 3 \,\mathrm{d}^{7} 4 \,\mathrm{s}^{2}\)is cobalt, a transition metal known for variable oxidation states. This is because transition metals can utilize electrons from both their outer and penultimate d orbital for bonding.

Key aspects of oxidation states include:

• Transition metals, like cobalt, exhibit multiple oxidation states due to their d electrons.
• The oxidation state is central to redox reactions where electron transfer occurs.
• Complexes involving transition metals often show varied colors due to different oxidation states.

The understanding of oxidation states is vital in predicting the outcome of chemical reactions including the stability, reactivity, and color properties of compounds.