Problem 119 - A Complete Resource Book in Chemistry for JEE Main

Question

Properties that are directly or indirectly related to the electronic configuration of the elements and show a regular gradation when we move from left to right in a period or form top to bottom in a group are called periodic properties. Some of these properties are ionization energy, electron affinity and electronegativity Which of the following is arranged in the order of decreasing electropositive character ? (a) \(\mathrm{Fe}, \mathrm{Mg}, \mathrm{Cu}\) (b) \(\mathrm{Mg}, \mathrm{Cu}, \mathrm{Fe}\) (c) \(\mathrm{Mg}, \mathrm{Fe}, \mathrm{Cu}\) (d) \(\mathrm{Cu}, \mathrm{Fe}, \mathrm{Mg}\)

Step-by-Step Solution

Answer

Option (c) Mg, Fe, Cu is in the order of decreasing electropositive character.

Step 1: Understanding Electropositive Character

Electropositive character of an element refers to its tendency to lose electrons and form positive ions. This is often associated with metals found on the left side of the periodic table. The more electropositive an element, the more metallic it is.

Step 2: Identifying Electropositive Ordered Elements

Among the given elements, Magnesium (Mg), Iron (Fe), and Copper (Cu), Magnesium is the most electropositive, followed by Iron, and then Copper. This is because Magnesium is an alkaline earth metal, which are generally more electropositive than transition metals like Iron and Copper.

Step 3: Analyzing the Given Options

We must arrange the elements in order of decreasing electropositive character: starting with the most electropositive metal and ending with the least. The order is: Mg > Fe > Cu.

Step 4: Matching with the Given Options

Compare the order obtained (Mg, Fe, Cu) with the provided options. Option (c) is Mg, Fe, Cu, which matches our determined order of decreasing electropositive character.

Key Concepts

Electropositive Character

Electropositive character refers to the ability of an element to lose electrons and form positive ions or cations. Generally, elements with high electropositive character are found in the leftmost parts of the periodic table, particularly among the alkali metals and alkaline earth metals. These elements tend to have few valence electrons, making it easier for them to lose electrons and participate in metallic bonding, which strengthens the metallic properties.

Electropositive elements are usually metals. For example, magnesium (Mg), which is a typical metal that readily loses two electrons to form the cation \( \mathrm{Mg}^{2+} \). The higher the electropositive character, the more metallic the element behaves. Elements like Mg have lower ionization energies compared to transition metals, facilitating easier electron loss.

Electronic Configuration

Electronic configuration is the arrangement of electrons in an element's atomic orbitals. This configuration is foundational to understanding an element's chemical properties and reactivity. Elements in the same group of the periodic table have similar electronic configurations, which results in similar chemical behaviors.

For instance, the electronic configuration of magnesium is \( 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \). This highlights that magnesium tends to lose its two 3s electrons easily to form a stable \( \mathrm{Mg}^{2+} \) ion, reflecting its high electropositive character. On the other hand, transition metals like iron and copper have more complex configurations that include partially filled d-subshells. This affects their ionization energies and electropositive character, with such configurations generally resulting in higher ionization energies than the more straightforward configurations seen in alkaline earth metals.

Metals in Periodic Table

Metals are prevalent in the periodic table and are primarily found on the left side. They exhibit characteristic properties such as good electrical conductivity, malleability, ductility, and a shiny appearance. Metals are divided into categories: alkali metals, alkaline earth metals, transition metals, and post-transition metals.

Alkali metals and alkaline earth metals are notably more electropositive than transition metals. As an example, considering the question of electropositive order among Mg, Fe, and Cu, magnesium is an alkaline earth metal. This classification helps understand why it is more electropositive compared to iron and copper that are transition metals. Transition metals like iron (Fe) and copper (Cu) have partially filled d-subshells that complicate their ability to lose electrons as easily as alkaline metals, thus, they tend to exhibit lower electropositive character compared to elements like magnesium.