Question

Zinc does not show variable valency, because (a) its d-subshell is incomplete (b) it is relatively soft metal (c) its d-subshell is complete (d) it has two electrons in outermost shell \eta. the reaction

Short answer

Zinc does not show variable valency because its d-subshell is complete, option (c).

Step-by-step solution

Understand the Concept of Variable Valency

Variable valency is a property of some elements to exhibit different valency in different compounds. It primarily occurs in elements with incompletely filled d-subshells, allowing for various oxidation states.

Analyze Zinc's Electron Configuration

Zinc's atomic number is 30, and its electron configuration is \([Ar] \, 3d^{10} 4s^2\). Notice that the 3d subshell is completely filled with 10 electrons.

Evaluate the Complete d-subshell

Since the d-subshell is complete, zinc is stable and does not commonly change its valency because there are no partially filled subshells for additional electron configurations.

Review Other Options

Option (a) and (d) do not relate to the concept of variable valency. Option (b) describes a physical property that is not relevant here. Only option (c) directly explains why zinc does not show variable valency.

Choose the Correct Answer

Based on the analysis, zinc does not show variable valency because its d-subshell is complete. Therefore, the correct answer is option (c).

Key concepts

Electron Configuration

The electron configuration of an element is a description of how electrons are distributed in its atomic orbitals. This distribution follows a certain order defined by energy levels and subshells, which helps in predicting various chemical properties of the element. For the element Zinc, which has an atomic number of 30, the electron configuration is given by \( [Ar] \, 3d^{10} \, 4s^2 \). Here, \( [Ar] \) represents the noble gas core configuration of Argon, which simplifies the notation for elements with a higher number of electrons.

• The notation \( 3d^{10} \) tells us that the d-subshell in the third energy level is fully occupied with 10 electrons.
• The \(4s^2\) part indicates two electrons in the 4s subshell, which are typically the electrons involved in bonding.

Understanding the electron configuration is key to predicting how Zinc behaves in a chemical reaction, as it dictates the likelihood of an element to form bonds and exhibit different properties.

d-subshell

The d-subshell is one of the types of atomic subshell present in atoms with three or more electron shells. It can hold a maximum of 10 electrons. Subshells are composed of orbitals, and for the d-subshell, there are five orbitals available. Within the periodic table, elements belonging to the transition metals usually have their properties dictated by these d-subshells. This is because:

• The d-subshell plays a critical role in the characteristics of transition metals by allowing electrons to move freely among orbitals.
• The movement and availability of these electrons enable these metals to exhibit different oxidation states.

In the case of Zinc, its 3d-subshell is completely filled with 10 electrons, leaving no room for variation in its electron configurations. This is key to understanding why Zinc doesn’t exhibit variable valency unlike other transition metals like iron or copper, which have partially filled d-subshells allowing variable oxidation states.

Zinc Chemistry

Zinc is a versatile metal primarily known for its role in protective coatings on iron and steel and as a constituent in various alloys. A key feature of its chemical behavior is its lack of variable valency, which is unusual for a transition metal. Here are some important points about Zinc's chemistry:

• Zinc primarily exhibits a +2 oxidation state due to the removal of its two 4s electrons.
• Its complete 3d-subshell makes it chemically stable and resistant to changing its oxidation state.

Despite being a transition metal, the fully filled d-subshell means Zinc does not engage in the electron exchange processes typical of other transition elements. This trait allows it to form stable and predictable compounds. Zinc’s consistent behavior makes it invaluable in numerous industrial applications, from galvanization to being a vital trace element in biological processes.

Oxidation States

Oxidation states, or oxidation numbers, describe the degree of oxidation of an atom within a compound. That is, it indicates the number of electrons an atom can gain, lose, or share when it reacts to form compounds. Understanding oxidation states is pivotal in grasping the chemical reactions and bonding capabilities of an element. In the context of Zinc:

• Zinc exhibits a stable oxidation state of +2, meaning it typically loses two electrons during chemical reactions.
• The +2 state is favored due to the removal of Zinc's 4s electrons, while the 3d electrons remain unaffected.

This stable oxidation state is intrinsically linked to its full d-subshell, as the lack of partially filled d orbitals restricts Zinc from forming variable oxidation states. Such a straightforward oxidation state is beneficial for its usage in predicting and controlling the outcomes of chemical reactions where Zinc is involved. This constancy helps make Zinc compounds reliable for industrial and biological usage.