Question

Some ions do not have a corresponding neutral atom that has the same electron configuration. For each of the following ions, identify the neutral atom that has the same number of electrons and determine if this atom has the same electron (d) \(\mathrm{Zn}^{2+}\) configuration. (a) \(\mathrm{Cl}^{-}\), (b) \(\mathrm{Sc}^{3+}\) (c) \(\mathrm{Fe}^{2+}\) (e) \(\mathrm{Sn}^{4+}\)

Short answer

(a) \(\mathrm{Cl}^{-}\) has the same electron configuration as the neutral atom Argon (Ar). (b) \(\mathrm{Sc}^{3+}\) has the same electron configuration as the neutral atom Argon (Ar). (c) \(\mathrm{Fe}^{2+}\) does not have the same electron configuration as any neutral atom. (d) \(\mathrm{Zn}^{2+}\) does not have the same electron configuration as any neutral atom. (e) \(\mathrm{Sn}^{4+}\) has the same electron configuration as the neutral atom Palladium (Pd).

Step-by-step solution

Identify the number of electrons in each ion

For each ion, the number of electrons is equal to its atomic number minus the charge (for positively charged ions) or plus the charge (for negatively charged ions). We can identify the atomic number of an element by referring to the periodic table. (a) \(\mathrm{Cl}^-\) has an atomic number of 17, so it has 18 electrons. (b) \(\mathrm{Sc}^{3+}\) has an atomic number of 21, so it has 18 electrons. (c) \(\mathrm{Fe}^{2+}\) has an atomic number of 26, so it has 24 electrons. (d) \(\mathrm{Zn}^{2+}\) has an atomic number of 30, so it has 28 electrons. (e) \(\mathrm{Sn}^{4+}\) has an atomic number of 50, so it has 46 electrons.

Identify the neutral atoms with the same number of electrons

Now that we have the number of electrons for each ion, we can find the neutral atoms with the same number of electrons. These atoms will have an atomic number equal to the number of electrons. (a) A neutral atom with 18 electrons is Argon (Ar). (b) A neutral atom with 18 electrons is Argon (Ar). (c) A neutral atom with 24 electrons is Chromium (Cr). (d) A neutral atom with 28 electrons is Nickel (Ni). (e) A neutral atom with 46 electrons is Palladium (Pd).

Compare electron configurations

We can now compare the electron configurations of each ion with its corresponding neutral atom to determine if they have the same electron configuration. (a) \(\mathrm{Cl}^-\) and \(\mathrm{Ar}\): Both have the electron configuration [Ne]3s\(^2\)3p\(^6\), so their electron configurations are the same. (b) \(\mathrm{Sc}^{3+}\) and \(\mathrm{Ar}\): Sc has the electron configuration [Ar]3d\(^1\)4s\(^2\), while Ar has the electron configuration [Ne]3s\(^2\)3p\(^6\). When Sc loses 3 electrons, it becomes \(\mathrm{Sc}^{3+}\) with the electron configuration [Ne]3s\(^2\)3p\(^6\), which is the same as Ar's electron configuration. (c) \(\mathrm{Fe}^{2+}\) and \(\mathrm{Cr}\): Fe has the electron configuration [Ar]3d\(^6\)4s\(^2\), while Cr has the electron configuration [Ar]3d\(^5\)4s\(^1\). When Fe loses 2 electrons, it becomes \(\mathrm{Fe}^{2+}\) with the electron configuration [Ar]3d\(^6\), which is not the same as Cr's electron configuration. (d) \(\mathrm{Zn}^{2+}\) and \(\mathrm{Ni}\): Zn has the electron configuration [Ar]3d\(^{10}\)4s\(^2\), while Ni has the electron configuration [Ar]3d\(^8\)4s\(^2\). When Zn loses 2 electrons, it becomes \(\mathrm{Zn}^{2+}\) with the electron configuration [Ar]3d\(^{10}\), which is not the same as Ni's electron configuration. (e) \(\mathrm{Sn}^{4+}\) and \(\mathrm{Pd}\): Sn has the electron configuration [Kr]4d\(^{10}\)5s\(^2\)5p\(^2\), while Pd has the electron configuration [Kr]4d\(^{10}\). When Sn loses 4 electrons, it becomes \(\mathrm{Sn}^{4+}\) with the electron configuration [Kr]4d\(^{10}\), which is the same as Pd's electron configuration. Thus, the neutral atoms with the same electron configuration as the given ions are: (a) \(\mathrm{Cl}^{-}\) - Argon (Ar) (b) \(\mathrm{Sc}^{3+}\) - Argon (Ar) (c) \(\mathrm{Fe}^{2+}\) - No neutral atom with the same electron configuration (d) \(\mathrm{Zn}^{2+}\) - No neutral atom with the same electron configuration (e) \(\mathrm{Sn}^{4+}\) - Palladium (Pd)

Key concepts

Neutral Atoms

Neutral atoms are fundamental pieces of chemistry and understanding them is key to grasping electron configurations. A neutral atom has an equal number of protons and electrons, resulting in no overall charge. The balance between positively charged protons and negatively charged electrons keeps these atoms neutral.
Neutral atoms are represented in the periodic table where each element displays its atomic number, which corresponds to the number of protons as well as electrons in a neutral state.
Understanding neutral atoms helps us in identifying similarities and differences in electron configurations compared to charged ions.

Periodic Table

The periodic table is a powerful tool. It organizes elements based on their atomic number, electron configurations, and recurring chemical properties. The table's arrangement allows us to predict how an element might behave in various chemical reactions.
Each element's atomic number indicates how many electrons are present in a neutral atom. This crucial information can help determine electron configuration. For example, the element Chlorine ( Cl) is located in the periodic table with an atomic number of 17, implying 17 electrons in its neutral state.

• The periodic table allows comparison between elements.
• It helps identify trends such as reactivity and electron affinity.
• Assists in deducing the electron configuration of ions compared to neutral atoms.

Ions

Ions are atoms or molecules that have gained or lost electrons, giving them a net charge. This charge is what differentiates ions from neutral atoms. There are two main types:
- **Cations**: These are positively charged ions formed by losing electrons. For instance, Zn} ^{2+} } is a cation derived from losing two electrons from a zinc atom.
- **Anions**: Negatively charged ions created by gaining electrons. For example, Cl }^{- } becomes an anion by gaining an extra electron.
By understanding ions, we can compare their electron configurations with those of neutral atoms. This helps in identifying which elements have similar electron configurations even when they're in ionic forms.

Electron Count

Counting electrons is essential when exploring neutral atoms and ions. The electron count changes based on whether an atom is neutral or has gained or lost electrons to become an ion.
For ions:

• **Positive charge ( +1, +2, etc.)**: Subtract electrons from the atomic number. E.g., Scandium ( Sc } ^{3+ }) becomes 18 electrons due to losing three electrons.
• **Negative charge ( -1, -2, etc.)**: Add electrons to the atomic number. E.g., Chlorine ( Cl }^{-}) becomes 18 electrons due to gaining an extra electron.

Knowing the electron count enables us to identify similar electron configurations among different elements and ions. This understanding is crucial for solving complex chemistry problems involving ion electron configurations.