Question

Why does chromium exhibit several oxidation states in its compounds, whereas aluminum exhibits only the \(+3\) oxidation state?

Short answer

Chromium exhibits several oxidation states in its compounds because it has both 3d and 4s electrons available for bonding, while aluminum exhibits only the +3 oxidation state because it has only three valence electrons (two 3s and one 3p) available for bonding. The various oxidation states of chromium are due to the removal of different combinations of 4s and 3d electrons, whereas aluminum loses all three valence electrons resulting in a +3 oxidation state. The difference in oxidation states between the two elements is mainly due to their electronic configurations.

Step-by-step solution

Electronic Configuration

First, let's find out the electronic configurations of chromium (Cr) and aluminum (Al). Chromium has an atomic number of 24, while aluminum has an atomic number of 13. So, their configurations are as follows: - Chromium (Cr): \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^5\) - Aluminum (Al): \(1s^2 2s^2 2p^6 3s^2 3p^1\)

Identify Oxidation States in Chromium

Chromium has several oxidation states because it has both 3d and 4s electrons available for bonding. Some common oxidation states of chromium include +2, +3, and +6. In these oxidation states, the following electron configurations occur: - Cr(+2): \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^4\) - Cr(+3): \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^3\) - Cr(+6): \(1s^2 2s^2 2p^6 3s^2 3p^6\) The various oxidation states of chromium are due to the removal of different combinations of 4s and 3d electrons for bonding purposes.

Identify Oxidation State in Aluminum

Aluminum exhibits only the +3 oxidation state. In this state, its electron configuration becomes: - Al(+3): \(1s^2 2s^2 2p^6\) Aluminum loses its three valence electrons (two 3s electrons and one 3p electron) during the bonding process. Its other electrons are in the inner shells and are not involved in bonding.

Explain the Difference in Oxidation States

Chromium exhibits several oxidation states due to its 3d and 4s electrons, which are available for bonding. Depending on the specific compound, chromium can lose different combinations of these electrons, resulting in various oxidation states. On the other hand, aluminum has only three valence electrons (two 3s and one 3p) available for bonding, and it loses all of them, resulting in a +3 oxidation state. Its core electrons (1s and 2s) are not involved in bonding, and its electron configuration doesn't allow for multiple oxidation states like chromium. In summary, the difference in oxidation states between chromium and aluminum is mainly due to their electronic configurations and the availability of 3d and 4s electrons in the case of chromium, while only having valence electrons in 3s and 3p orbitals for aluminum.