Problem 35 - Chemistry The Molecular Nature of Matter

Question

Titanium burns in pure nitrogen to form TiN. What are the oxidation states of titanium and nitrogen in TiN?

Step-by-Step Solution

Answer

The oxidation state of titanium (Ti) in TiN is +3, and the oxidation state of nitrogen (N) is -3.

Step 1: Identify the Compound

Identify the compound in question, which is titanium nitride (TiN).

Step 2: Determine Oxidation State of Nitrogen

By convention, the oxidation state of nitrogen in a compound is typically -3, unless the compound contains peroxides or other unusual bonding arrangements.

Step 3: Determine Oxidation State of Titanium

Since the compound is neutral, and we know that nitrogen has an oxidation state of -3, the oxidation state of titanium must balance this to make the sum of oxidation states equal to zero. If nitrogen is -3 and there’s only one nitrogen atom, titanium must be +3.

Key Concepts

Chemical Bonding

Chemical bonding is the force that holds atoms together in molecules and compounds. It's one of the key concepts in chemistry and plays a critical role in determining the structure, properties, and behavior of substances. Bonds are formed through the sharing or transfer of electrons between atoms.

There are several types of chemical bonds, including ionic, covalent, and metallic bonds.

• Ionic bonding occurs when electrons are transferred from one atom to another, resulting in positively and negatively charged ions that attract each other.
• Covalent bonding is when atoms share pairs of electrons, creating a strong bond between them.
• Metallic bonding involves the sharing of free electrons amongst a lattice of metal ions, creating a 'sea' of electrons.

In the context of titanium nitride (TiN), the bond between titanium (Ti) and nitrogen (N) is predominantly ionic, with Ti giving up electrons to N, because N has a higher electronegativity and a tendency to attract electrons.

Oxidation State Determination

Determining the oxidation state of an atom in a compound is essential for understanding the electron distribution within that compound. Oxidation state, also known as oxidation number, is a concept that provides an accounting scheme for electrons in the atoms of a molecule or ion in terms of a hypothetical charge that an atom would have if all bonds to atoms of different elements were completely ionic.

Here are simple rules to follow for the determination of oxidation states:

• The oxidation state of a pure element is always zero.
• For a simple monoatomic ion, the oxidation state is equal to the charge of the ion.
• In a molecule or compound, the sum of oxidation states must equal the overall charge of the molecule or compound.
• Some elements have more common oxidation states based on their position in the periodic table and their typical bonding patterns.

When applying these rules to TiN, we can deduce that since TiN is a neutral compound and hence the sum of oxidation states must equal zero, and if nitrogen commonly has an oxidation state of -3, then titanium must therefore be in the +3 oxidation state in order to balance the compound's overall charge.

Titanium Nitride (TiN)

Titanium nitride (TiN) is a compound consisting of titanium and nitrogen, renowned for its hardness and often used in coatings to protect industrial tools. Its golden color also makes it popular for jewelry plating.

From a chemical perspective, TiN is a result of the reaction between titanium and nitrogen at high temperatures, whereby titanium burns in an atmosphere of pure nitrogen to form this compound. The bonding in titanium nitride can be described as predominantly ionic with some covalent character due to the sharing of electrons between Ti and N atoms. Titanium, as we've determined from the oxidation state analysis, is in the +3 state, donating three of its valence electrons to nitrogen, which in turn takes on a -3 oxidation state. This reflects the strong need for nitrogen to gain electrons in order to achieve a stable electronic configuration similar to that of the noble gases. It is the surrendering and acceptance of these electrons that not only define the chemical characteristic of TiN but also its physical properties such as high melting point and great hardness.