Predict the number of unpaired electrons for each of the following.
(c) Mn3+
(d) Cr2+

Verified step by step guidance

1. Step 1: Determine the electron configuration of the neutral atom. For Mn (Manganese), the electron configuration is [Ar] 4s2 3d5. For Cr (Chromium), the electron configuration is [Ar] 4s1 3d5.
2. Step 2: Remove electrons to account for the positive charge. For Mn3+, remove three electrons. The first two electrons are removed from the 4s orbital, and the third electron is removed from the 3d orbital, resulting in the electron configuration [Ar] 3d4. For Cr2+, remove two electrons. The first electron is removed from the 4s orbital, and the second electron is removed from the 3d orbital, resulting in the electron configuration [Ar] 3d4.
3. Step 3: Determine the number of unpaired electrons by looking at the electron configuration. For Mn3+, there are four unpaired electrons in the 3d orbital. For Cr2+, there are also four unpaired electrons in the 3d orbital.
4. Step 4: Remember that unpaired electrons are responsible for the magnetic properties of an atom or ion. The more unpaired electrons, the stronger the magnetic properties.
5. Step 5: Practice predicting the number of unpaired electrons for different atoms and ions to become more comfortable with this process.

Key Concepts

Electron Configuration

Electron configuration describes the distribution of electrons in an atom's orbitals. For transition metals, this involves filling the 3d and 4s orbitals according to the Aufbau principle, Hund's rule, and the Pauli exclusion principle. Understanding the electron configuration of an element is crucial for predicting its chemical properties, including the number of unpaired electrons.

Unpaired Electrons

Unpaired electrons are electrons that occupy an orbital alone rather than in pairs. The presence of unpaired electrons in an atom contributes to its magnetic properties and reactivity. In transition metals, the number of unpaired electrons can be determined by examining the electron configuration and identifying how many electrons are in the d orbitals without a partner.

Oxidation States

Oxidation states indicate the degree of oxidation of an atom in a compound, reflecting the number of electrons lost or gained. For transition metals, oxidation states can affect the electron configuration significantly. For example, Mn in Mn3+ has lost three electrons, which alters its electron configuration and the number of unpaired electrons compared to its neutral state.