Look at the location in the periodic table of elements A, B, C, and D. What is the electron configuration of the transition metal in each of the following ions?  
(a) A²⁺
(b) B⁺

Verified step by step guidance

1. Step 1: Identify the atomic number of the transition metal. The atomic number is the number of protons in an atom, which also equals the number of electrons in a neutral atom. You can find this information in the periodic table.
2. Step 2: Write the electron configuration for the neutral atom. The electron configuration describes the distribution of electrons in an atom's electron shells. It follows the Aufbau principle, which states that electrons fill the lowest energy levels first. For example, the electron configuration of a neutral atom of iron (Fe), which is a transition metal with an atomic number of 26, is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶.
3. Step 3: Adjust the electron configuration for the ion. When a transition metal ion loses electrons, it first loses the electrons in the highest energy level (the outermost shell). In the case of a Fe²⁺ ion, it would lose the two 4s electrons, resulting in the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶.
4. Step 4: Repeat steps 1-3 for each ion. Remember that the charge of the ion indicates the number of electrons lost (for positive ions) or gained (for negative ions).
5. Step 5: Keep in mind that some transition metals can have exceptions to the Aufbau principle due to the stability of half-filled or fully filled d sub-levels. For example, chromium (Cr) and copper (Cu) have electron configurations that differ from what would be predicted by the Aufbau principle.

Key Concepts

Electron Configuration

Electron configuration describes the distribution of electrons in an atom's orbitals. It follows the Aufbau principle, which states that electrons fill lower-energy orbitals first. For transition metals, the electron configuration can be complex due to the involvement of d orbitals, and it is crucial to understand how to write configurations for both neutral atoms and their ions.

Ionic Charge and Electron Loss

Ionic charge indicates the number of electrons an atom has lost or gained to form an ion. For example, a 2+ charge means the atom has lost two electrons. In transition metals, the loss of electrons typically occurs from the outermost s and d orbitals, which is essential for determining the correct electron configuration of the resulting ion.

Periodic Table and Transition Metals

The periodic table organizes elements based on their atomic number and electron configurations. Transition metals are found in groups 3 to 12 and are characterized by their ability to form variable oxidation states. Understanding the position of elements A, B, C, and D in the periodic table helps predict their electron configurations and the behavior of their ions.