Write the electron configuration for each of the following ions, and determine which ones possess noble-gas configurations: (a) Be2+, (b) Mn2+, (c) Cd2+, (d) Fe3+, (e) Tl+, (f) At-.

Verified step by step guidance

1. Identify the atomic number of each element to determine the number of electrons in the neutral atom. For ions, adjust the electron count based on the charge of the ion (subtract electrons for positive charges and add electrons for negative charges).
2. Write the electron configuration for each ion using the adjusted electron count. Start filling the orbitals from the lowest energy level to the highest, following the Aufbau principle, and apply Hund's rule and the Pauli exclusion principle as necessary.
3. For Be2+, remove two electrons from the neutral beryllium configuration. For Mn2+, remove two electrons from the neutral manganese configuration. For Cd2+, remove two electrons from the neutral cadmium configuration. For Fe3+, remove three electrons from the neutral iron configuration. For Tl+, remove one electron from the neutral thallium configuration. For At-, add one electron to the neutral astatine configuration.
4. Compare the resulting electron configurations of the ions to the electron configurations of the noble gases (He, Ne, Ar, Kr, Xe, Rn) to determine if any of the ions have noble-gas configurations.
5. Identify which ions have noble-gas configurations by checking if their electron configurations match exactly with one of the noble gases' electron configurations.

Key Concepts

Electron Configuration

Electron configuration describes the distribution of electrons in an atom or ion's atomic orbitals. It is represented using a notation that indicates the energy levels and sublevels occupied by electrons, following the Aufbau principle, Pauli exclusion principle, and Hund's rule. Understanding how to write electron configurations is essential for predicting chemical behavior and properties of elements and ions.

Ionic Charge and Electron Loss/Gain

Ionic charge refers to the net electrical charge an atom or ion carries due to the loss or gain of electrons. Cations are positively charged ions formed by losing electrons, while anions are negatively charged ions formed by gaining electrons. Knowing the charge of an ion is crucial for determining its electron configuration, as it directly affects the number of electrons present compared to the neutral atom.

Noble-Gas Configuration

Noble-gas configuration refers to an electron configuration that matches that of the nearest noble gas, characterized by a full outer electron shell. Atoms and ions with noble-gas configurations are generally more stable and less reactive. Identifying whether an ion possesses a noble-gas configuration helps in understanding its stability and reactivity in chemical reactions.