Question

For each of the following compounds, determine the electron configuration of the transition-metal ion. \((\mathbf{a})\) TiO, \((\mathbf{b}) \mathrm{TiO}_{2},(\mathbf{c}) \mathrm{NiO},(\mathbf{d}) \mathrm{ZnO}\) .

Short answer

The electron configurations of the transition-metal ions in the given compounds are: a) \(\mathrm{Ti^2+ : [Ar] \ 3d^2}\) b) \(\mathrm{Ti^4+ : [Ar]}\) c) \(\mathrm{Ni^2+ : [Ar] \ 3d^8}\) d) \(\mathrm{Zn^2+ : [Ar] \ 3d^{10}}\)

Step-by-step solution

a) TiO

Before finding the electron configuration of the transition-metal ion, let's first determine the oxidation state of Ti in TiO: Oxygen has an oxidation state of -2, so Ti must have an oxidation state of +2 to balance the charges in the compound. Now, we can write the electron configuration of the neutral Ti atom and then remove the appropriate number of electrons to account for the oxidation state: The electron configuration of the neutral Ti atom is: \[ \mathrm{[Ar] 3d^2 4s^2}\] The Ti²⁺ ion would have an electron configuration where we remove two electrons: \[ \mathrm{[Ar] 3d^2}\]

b) TiO₂

To find the oxidation state of Ti in TiO₂, we need to consider that there are two oxygen atoms present in the compound: Each oxygen atom has an oxidation state of -2, making a total oxidation state of -4. Therefore, Ti must have an oxidation state of +4 to balance the charges in the compound. Using the electron configuration of the neutral Ti atom from the previous step, we can remove four electrons to account for the oxidation state: The Ti⁴⁺ ion would have an electron configuration: \[ \mathrm{[Ar] }\]

c) NiO

First, we determine the oxidation state of Ni in NiO: As it's been mentioned before, oxygen has an oxidation state of -2. Therefore, Ni must have an oxidation state of +2 to balance the charges in the compound. The electron configuration of a neutral Ni atom is: \[ \mathrm{[Ar] 3d^8 4s^2}\] The Ni²⁺ ion would have an electron configuration where we remove two electrons: \[ \mathrm{[Ar] 3d^8}\]

d) ZnO

Lastly, let's determine the oxidation state of Zn in ZnO: Oxygen exhibits an oxidation state of -2. Thus, Zn must have an oxidation state of +2 to balance the charges in the compound. The electron configuration of a neutral Zn atom is: \[ \mathrm{[Ar] 3d^{10} 4s^2}\] The Zn²⁺ ion would have an electron configuration where we remove two electrons: \[ \mathrm{[Ar] 3d^{10}}\] In summary, the electron configurations of the transition-metal ions in the given compounds are: a) \(\mathrm{Ti^2+ : [Ar] \ 3d^2}\) b) \(\mathrm{Ti^4+ : [Ar]}\) c) \(\mathrm{Ni^2+ : [Ar] \ 3d^8}\) d) \(\mathrm{Zn^2+ : [Ar] \ 3d^{10}}\)

Key concepts

Transition Metal Ions

Transition metals are unique in the periodic table because they can form ions with different charges. These ions result from the loss of electrons, typically from the outermost shell. Transition metal ions are generally formed when these metals react with non-metals, such as oxygen, in our examples. The charge on a transition metal ion is determined by the number of electrons removed from the metal atom.

For instance, in the compound TiO, titanium (Ti) forms a Ti²⁺ ion by losing two electrons. This occurs because oxygen has a consistent -2 charge, requiring titanium to balance it with a +2 charge.

Understanding the nature of transition metal ions is critical because it allows us to predict and explain the properties of the compounds they form, including their color, magnetism, and reactivity.

Oxidation State

The oxidation state, also known as oxidation number, is an indicator of the degree of oxidation of an atom in a compound. It represents the number of electrons an atom gains or loses when forming a compound.

For example, in the compound TiO₂, oxygen has an oxidation state of -2, but there are two oxygen atoms, which total a -4 charge. Therefore, titanium must have an oxidation state of +4 to balance the charges, forming a Ti⁴⁺ ion.

This concept is especially important for transition metals because they often exhibit multiple oxidation states. Through knowing the oxidation state, we can make predictions about a transition metal's behavior in chemical reactions, such as which reactions it might undergo and how it interacts with other elements.

Compound Electron Configuration

Electron configuration is the arrangement of electrons in an atom's orbitals, and it determines how atoms react chemically. In transition metals, electron configurations are particularly important because these metals can often lose different numbers of d electrons.

For a neutral titanium (Ti) atom, the electron configuration is \([ \text{Ar} ] 3d^2 4s^2\). When it forms a Ti²⁺ ion as in TiO, it loses two electrons and the configuration becomes \([ \text{Ar} ] 3d^2\).

Similarly, nickel (Ni) in NiO forms a Ni²⁺ ion with the configuration \([ \text{Ar} ] 3d^8\), after losing two 4s electrons. Electron configurations reveal not just the number of valence electrons, but also insights into the potential reactivity and bonding behavior of transition metals.

Transition Metals Chemistry

Transition metals are elements found in the d-block of the periodic table and are known for their wide range of chemical behaviors. Their ability to form complex compounds, along with their varied oxidation states, contributes significantly to their chemistry.

For example, zinc (Zn) commonly forms Zn²⁺ ions, as seen in ZnO, because it typically loses two electrons. This behavior influences its participation in complex reactions and its role in catalysis.

Transition metals also exhibit unique properties such as variable hydration, colored compounds, and interesting magnetic properties. These interesting properties arise because of the way electrons are arranged and the subsequent behavior of these electrons during reactions. The chemistry of transition metals holds great significance in industries, from the manufacturing of paints and dyes to the development of new materials and catalysts.