Problem 2 - Chemistry and Chemical Reactivity

Question

Identify two transition metal ions with the following electron configurations. (b) \([\mathrm{Ar}] 3 d^{10}\) (a) \([\mathrm{Ar}] 3 d^{6}\) (c) \([\mathrm{Ar}] 3 d^{5}\) (d) \([\mathrm{Ar}] 3 d^{8}\)

Step-by-Step Solution

Answer

(a) Fe ion, (b) Zn ion, (c) Mn ion, (d) Ni ion.

Step 1: Review Electron Configuration

The electron configuration given in terms of the argon core \( [\mathrm{Ar}] \), which represents the configuration \(1s^2 2s^2 2p^6 3s^2 3p^6\). Transition metals typically involve changes in their \(3d\) subshells when they form ions, given that this block of the periodic table is defined by these subshells.

Step 2: Match Electron Configurations with Transition Metals

We need to find transition metals whose ions have electron configurations matching those provided. For this, adjust any potential ionic states to those that possess the stable states indicated:

Step 2a: Identify configuration (a) \\\( [\mathrm{Ar}] 3 d^6 \\\)

This configuration corresponds to iron (Fe) ion in its \( ext{Fe}^{2+} \) oxidation state. Iron has a neutral atom configuration of \( [\mathrm{Ar}] 3d^6 4s^2 \) and when it loses 2 electrons, it becomes \( [\mathrm{Ar}] 3d^6 \).

Step 2b: Identify configuration (b) \\\( [\mathrm{Ar}] 3 d^{10} \\\)

This matches the zinc (Zn) ion in its neutral state. Zn has \( [\mathrm{Ar}] 3d^{10} 4s^2\) in atomic form, but as an ion like \( ext{Zn}^{2+} \), it's usually referenced to a full \(3d^{10}\) block.

Step 2c: Find matching metal for (c) \\\( [\mathrm{Ar}] 3 d^5 \\\)

This could correctly pair with manganese (Mn) in ion form as \( ext{Mn}^{2+} \), because the neutral Mn is \( [\mathrm{Ar}] 3d^5 4s^2 \). Upon losing two \(4s\) electrons, it becomes \( [\mathrm{Ar}] 3 d^5 \).

Step 2d: Match configuration (d) \\\( [\mathrm{Ar}] 3 d^8 \\\)

This corresponds with nickel (Ni) in its \( ext{Ni}^{2+} \) state, where the neutral Ni is \( [\mathrm{Ar}] 3d^8 4s^2 \), losing two electrons (from \(4s\) orbital) results in \( [\mathrm{Ar}] 3d^8 \).

Key Concepts

Electron Configuration

Electron configuration is a way to represent the arrangement of electrons in an atom. For transition metals, the focus is mainly on the 3d subshell because that's where the most significant changes happen when ions are formed. Let's break it down further:

• The electron configuration notation starts with the principal quantum number, followed by the letter of the orbital type (s, p, d, f), and finally the number of electrons in that orbital.
• For example, \([\mathrm{Ar}] 3d^6\) represents six electrons in the 3d subshell after completing the configuration up to argon.
• This method assumes the electrons are filled in a particular order based on the energy levels of the orbitals, known as the Aufbau principle.

Understanding electron configurations is crucial when identifying transition metal ions and predicting their chemical behavior.

Oxidation States

Oxidation states play a critical role in understanding how transition metals form ions. Each oxidation state corresponds to a different electron configuration and results in unique chemical properties.

• Transition metals can have multiple oxidation states, meaning they can lose different numbers of electrons.
• For example, iron ( Fe) can be found in an oxidation state of Fe^{2+} or Fe^{3+}, each corresponding to different electron configurations.
• To find the oxidation state, you look at how many electrons are lost or gained compared to the neutral atom. For instance, the oxidation state Fe^{2+} implies the atom has lost two electrons from its neutral state.

It’s important to note these changes primarily occur in the 3d and 4s subshells of transition metals, affecting both their physical and chemical properties.

Periodic Table

The periodic table provides a systematic arrangement of elements, helping predict the behavior of transition metals and their ions based on their position.

• Transition metals are located in the d-block of the periodic table, signifying the filling of the d subshells.
• Their position in the periodic table indicates typical quantum numbers for the highest energy electrons they possess, usually found in the 3d subshell for the first transition series.
• Elements in the same group (vertical columns) generally have similar properties because they have the same number of electrons in their outer shell, which often translates to similar oxidation states.

The periodic table thus acts as a roadmap, guiding us in identifying electron configurations and oxidation states of transition metals.