Problem 55 - Chemistry The Central Science

Question

Give the number of (valence) \(d\) electrons associated with the central metal ion in each of the following complexes: (a) \(\mathrm{K}_{3}\left[\mathrm{TiCl}_{6}\right]\) (b) \(\mathrm{Na}_{3}\left[\mathrm{Co}\left(\mathrm{NO}_{2}\right)_{6}\right],\) (c) \(\left[\mathrm{Ru}(\mathrm{en})_{3}\right] \mathrm{Br}_{3},\) (d) \([\mathrm{Mo}(\mathrm{EDTA})] \mathrm{ClO}_{4},(\mathrm{e}) \mathrm{K}_{3}\left[\mathrm{ReCl}_{6}\right] .\)

Step-by-Step Solution

Answer

The number of valence d electrons associated with the central metal ion in each complex is: (a) 1 (b) 6 (c) 5 (d) 5 (e) 4

Step 1: Identify the central metal ion in each complex

For each of the given complexes, identify the central metal ion: (a) K3[TiCl6]: Ti (b) Na3[Co(NO2)6]: Co (c) [Ru(en)3]Br3: Ru (d) [Mo(EDTA)]ClO4: Mo (e) K3[ReCl6]: Re

Step 2: Determine the oxidation state of the central metal ion

For each complex, write out the charge balance equation and solve for the oxidation state of the central metal ion. (a) K3[TiCl6]: 3(+1) + x + 6(-1) = 0 -> x = +3 (Ti) (b) Na3[Co(NO2)6]: 3(+1) + x + 6(-1) = 0 -> x = +3 (Co) (c) [Ru(en)3]Br3: x + 3(-1) = 0 -> x = +3 (Ru) (d) [Mo(EDTA)]ClO4: x + (-1) = 0 -> x = +1 (Mo) (e) K3[ReCl6]: 3(+1) + x + 6(-1) = 0 -> x = +3 (Re)

Step 3: Determine the number of valence d electrons for each central metal ion

Using the oxidation state from step 2, we can now find the number of valence d electrons: (a) Ti(III): There are 4 valence electrons for Ti in its ground state, so losing 3 will result in 1 d electron left. (b) Co(III): There are 9 valence electrons for Co in its ground state, so losing 3 will result in 6 d electrons left. (c) Ru(III): There are 8 valence electrons for Ru in its ground state, so losing 3 will result in 5 d electrons left. (d) Mo(I): There are 6 valence electrons for Mo in its ground state, so losing 1 will result in 5 d electrons left. (e) Re(III): There are 7 valence electrons for Re in its ground state, so losing 3 will result in 4 d electrons left. In conclusion, the number of valence d electrons associated with the central metal ion in each complex is: (a) 1 (b) 6 (c) 5 (d) 5 (e) 4

Key Concepts

Valence Electrons

Valence electrons play a pivotal role in determining the chemical behavior of atoms. They are the electrons that reside in the outermost shell of an atom. For coordination compounds, it is particularly important to understand the valence d electrons of transition metals.
These electrons affect the metal's bonding and placement in the spectral series. Valence d electrons are largely responsible for the formation of coordination complexes. In the given exercise, identifying valence d electrons for transition metals like Titanium (\( \text{Ti} \)), Cobalt (\( \text{Co} \)), and others, helps in predicting the properties of these complexes.

• The number of valence electrons influences the oxidation state and electron configuration.
• It determines how metals interact with ligands in a complex.
• Valence electrons dictate the geometry and overall stability of a compound.

Understanding these aspects allow you to theorize how metals bond, react, and eventually contribute to a compound's chemical makeup.

Oxidation States

Oxidation states indicate the degree of oxidation of an element within a compound. They tell us how many electrons an atom has gained or lost in forming a compound. In coordination chemistry, calculating the oxidation state of the central metal ion gives valuable insight into the compound's structure and reactivity.
Using oxidation states, one can understand the electron flow in reaction equations, thereby predicting the molecule's behavior. For instance, in the compound \[ \text{K}_3[\text{TiCl}_6] \], by calculating the sum of known charges of potassium and chloride, you determine Titanium's oxidation state is +3.

• Oxidation state helps determine the charge of the entire complex.
• It gives a way to balance out the molecular charge using known component charges.
• Understanding oxidation states is crucial for predicting a compound's reactivity and potential chemical shifts.

Give attention to the neutralizing ions around the central metal for a more accurate depiction of a compound's ionic structure.

Transition Metals

Transition metals are elements that have partially filled d subshells. They are unique due to their ability to use those d electrons in bonding, which leads to the formation of colorful and complex coordination compounds. Transition metals like Titanium (\( \text{Ti} \)), Cobalt (\( \text{Co} \)), and Molybdenum (\( \text{Mo} \)) are central to the exercise.
This partially filled d-orbital mechanism imparts a variety of magnetic and catalytic properties.

• Transition metals exhibit variable oxidation states, enabling them to form diverse compounds.
• Their presence in a complex impacts the stability and color due to d-d electron transitions, which absorb specific wavelengths of light.
• The ultimate count of valence d electrons in transition metals allows the exploration of entirely new chemical behaviors.

These metals act as pivotal points for forming advanced compounds due to their unique electron configurations. Appreciating the chemistry of transition metals opens the door to understanding their versatility in both natural and synthesized materials.