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) \(\mathrm{Sn}^{4+}\)

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.

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).

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)