Question

Which of the following contains a metal ion that does not have a noble gas electron configuration? $$ \mathrm{AgCl}, \mathrm{BaCl}_{2}, \mathrm{TiO}_{2}, \mathrm{ScF}_{3}, \mathrm{KNO}_{3} $$

Short answer

The metal ion in \(\mathrm{TiO}_2\) (Ti⁴⁺) does not have a noble gas electron configuration, as its electron configuration is [Ar] \(3d^0\). All other metal ions in the given compounds have noble gas electron configurations.

Step-by-step solution

Write electron configurations for each metal ion

First, we will find the electron configurations for the metal ions present in each compound: - \(\mathrm{Ag}\) in \(\mathrm{AgCl}\): Silver has an atomic number of 47; its neutral electron configuration is [Kr] \(4d^{10}5s^1\). When it loses one electron to form the Ag+ ion, it becomes [Kr] \(4d^{10}\). - \(\mathrm{Ba}\) in \(\mathrm{BaCl}_2\): Barium has an atomic number of 56; its neutral electron configuration is [Xe] \(6s^2\). When it loses two electrons to form the Ba²⁺ ion, it becomes [Xe]. - \(\mathrm{Ti}\) in \(\mathrm{TiO}_2\): Titanium has an atomic number of 22; its neutral electron configuration is [Ar] \(4s^2 3d^2\). When it loses four electrons to form the Ti⁴⁺ ion, it becomes [Ar] \(3d^0\). - \(\mathrm{Sc}\) in \(\mathrm{ScF}_3\): Scandium has an atomic number of 21; its neutral electron configuration is [Ar] \(4s^2 3d^1\). When it loses three electrons to form the Sc³⁺ ion, it becomes [Ar]. - \(\mathrm{K}\) in \(\mathrm{KNO}_3\): Potassium has an atomic number of 19; its neutral electron configuration is [Ar] \(4s^1\). When it loses one electron to form the K⁺ ion, it becomes [Ar].

Determine which metal ion does not have a noble gas electron configuration

Now, we will examine each metal ion's electron configuration to see which one does not have the noble gas electron configuration: - \(\mathrm{Ag}^+\): [Kr] \(4d^{10}\) - This is a noble gas configuration as \(3d\) and \(4s\) orbitals are filled. - \(\mathrm{Ba}^{2+}\): [Xe] - This is a noble gas configuration. - \(\mathrm{Ti}^{4+}\): [Ar] \(3d^0\) - This is not a noble gas configuration as the \(3d\) orbitals are empty. - \(\mathrm{Sc}^{3+}\): [Ar] - This is a noble gas configuration. - \(\mathrm{K}^+\): [Ar] - This is a noble gas configuration.

Conclusion

The metal ion in \(\mathrm{TiO}_2\) (Ti⁴⁺) does not have a noble gas electron configuration, as its electron configuration is [Ar] \(3d^0\). All the other metal ions in the given compounds have noble gas electron configurations: Ag⁺, Ba²⁺, Sc³⁺, and K⁺.

Key concepts

Metal Ions

Metal ions are positively charged atoms formed when metals lose electrons. These ions play essential roles in various chemical reactions and compounds. For metal ions, understanding their electron configuration helps us determine their chemical behavior. Each metal ion can have different charges, also known as oxidation states, depending on how many electrons it loses during a reaction.

When metal ions form, they do so by shedding outer electrons to reach a more stable state. This process often leads them to adopt electron configurations akin to those of noble gases. Noble gases have complete valence electron shells, making them extremely stable and inert. Hence, many metal ions aim to achieve similar stability.

For example, in the exercise, different compounds have metals such as Ag in AgCl and Ba in BaCl₂. Each of these forms cations by losing electrons depending on its position in the periodic table, impacting its reactivity and types of bonds it can form.

Noble Gas Configuration

A noble gas configuration refers to an atoms's electron structure that matches one of the noble gases, located in Group 18 of the periodic table. Noble gases have full valence electron shells, typically giving them high stability. Many elements strive to achieve this stable electron configuration through the loss, gain, or sharing of electrons.

In chemical reactions, metals tend to lose electrons achieving electron configurations similar to the nearest noble gas. For instance:

• Silver ( Ag), when it forms an Ag⁺ ion, achieves the electron configuration of krypton ([Kr] 4d¹⁰).
• Barium ( Ba) in its Ba²⁺ state also adopts the electron configuration of xenon ([Xe]).
• Titanium ( Ti), however, as a Ti⁴⁺ ion, has a electron configuration [Ar] 3d⁰, which does not resemble any noble gas configuration.

This is critical in predicting and explaining why certain ions are more chemically stable than others. The elements often adjust their electron configurations in reactions for this stability, which is a core concept in understanding the behavior of metals and their ions.

Oxidation States

Oxidation states (or numbers) indicate the degree of oxidation of an atom in a chemical compound. This concept is essential when analyzing redox reactions, balancing chemical equations, and understanding the transfer of electrons between atoms.

The oxidation state of an element in its ion form equates to the charge it possesses. For metals, this number represents how many electrons have been lost to reach its current state. For example:

• Ag in AgCl is in the +1 oxidation state after losing one electron to become Ag⁺.
• Ba in BaCl₂ is in the +2 state after losing two electrons to form Ba²⁺.
• Ti in TiO₂ reaches a +4 state after losing four electrons, becoming Ti⁴⁺ with an electron configuration of [Ar] 3d⁰.

The oxidation state is a practical tool for predicting the possible compounds that an element can form.

Furthermore, understanding oxidation states helps elucidate reaction mechanisms. It is particularly important when dissecting why some elements do not attain noble gas configurations; their oxidation states reveal insights into the depth of electron involvement in reactions.