Question

Explain the following: (a) Transition elements form alloys. (b) Transition metals are usually hard solids but mercury exists as liquid at room temperature. (c) \(\mathrm{VCl}_{5}\) doesn't exist but \(\mathrm{VF}_{5}\) exists. (d) What are the characteristic properties of transition elements?

Short answer

Transition elements form alloys due to their similar atomic radii. Mercury exists as a liquid at room temperature due to weak bonding between its atoms. \( \mathrm{VCl}_{5} \) doesn't exist because chlorine can't form more than one covalent bond, but \( \mathrm{VF}_{5} \) exists as fluorine can exhibit both ionic and covalent bonding. Transition elements are characterized by variable oxidation states, good conductivity, formation of colored compounds, and paramagnetism.

Step-by-step solution

Explaining why transition elements form alloys

Transition elements can form alloys due to their similar atomic radii. Elements with similar atomic sizes can replace each other in their crystal lattice, leading to the formation of a solid solution of two or more metals, which is an alloy.

Discussing the state of mercury at room temperature

Mercury is unique among transition metals as it exists as a liquid at room temperature. This is due to the weak bonding between its atoms. While most metals, including transition metals, have a metallic bonding that results in a closely packed arrangement of atoms or ions, mercury’s electronic configuration results in a less effective overlap of its atomic orbitals and hence weaker bond strength.

Discussing why \( \mathrm{VCl}_{5} \) doesn't exist but \( \mathrm{VF}_{5} \) exists

Vanadium (V) is in group 5 of the periodic table and hence has 5 electrons in its outermost shell. It can therefore form compounds in which it exhibits a maximum state of oxidation of +5. Chlorine, a group 7 element, forms only one covalent bond with an atom of another element. Therefore, vanadium can't form \( \mathrm{VCl}_{5} \) because that would involve vanadium forming 5 covalent bonds with chlorine, which is not possible. Fluorine, on the other hand, is also a group 7 element but it can exhibit both ionic and covalent bonding. Thus, vanadium forms \( \mathrm{VF}_{5} \), in which it exhibits a +5 oxidation state.

Characteristic properties of transition elements

Transition elements have the following characteristic properties: They often exhibit variable oxidation states, they are usually good conductors of heat and electricity, they often form colored compounds, and they can have paramagnetic behavior due to the presence of unpaired electrons.

Key concepts

alloy formation

Alloy formation is a fascinating property of transition metals. These metals are quite adept at forming alloys because of their similar atomic radii. Imagine their atoms as having similar sizes, which makes it easier for them to swap places in each other's crystal lattice. This swapping creates a new solid mixture of metals, known as an alloy. Alloys often have enhanced properties compared to their component metals.
For example, steel is an alloy of iron and carbon, and it gains strength and durability from this combination. Transition metals, like chromium or nickel, can be added to steel to enhance its corrosion resistance.
A few key points about alloys in transition metals include:

• They often contain a mixture of different metals.
• The similar atomic sizes make it easier for alloys to form.
• Alloys tend to have improved physical properties.

variable oxidation states

The ability of transition metals to show variable oxidation states is one of their distinctive features. Oxidation states refer to the charge of the metal after it has lost or gained electrons. Transition metals can lose different numbers of electrons in different situations. This gives them the versatility to form a variety of compounds.
For example, iron can exist in ^(2+) and ^(3+) oxidation states in its compounds. These different states allow transition metals to undergo redox reactions, pivotal in industrial and biological processes.
Some highlights about oxidation states include:

• They provide versatility in forming various compounds.
• Manganese, as an example, exhibits oxidation states from +2 to +7.
• This flexibility contributes to their underlying utility in catalysis.

electronic configuration

Electronic configuration refers to the arrangement of electrons in an atom's electron shells. Transition metals have unique electronic configurations because they fill their d orbitals. These d orbitals can hold up to 10 electrons. After filling up the s orbitals of the previous shell, electrons start filling the d orbital, which is at a lower energy level. This configuration explains many properties of transition metals.
For example, the partially filled d orbitals allow transition metals to absorb specific frequencies of light, often leading them to form colorful compounds, which is a hallmark of these metals.
Key points regarding electronic configurations for transition metals:

• The d-level orbitals give these metals their typical behaviors.
• The electron arrangements lead to interesting chemical properties.
• Their configurations are responsible for the colored ions they often form.

paramagnetism

Paramagnetism in transition metals arises from the presence of unpaired electrons in their d orbitals. When an external magnetic field is applied, these unpaired electrons align with the field, causing the material to be attracted by the field. This tendency to align makes paramagnetic materials different from diamagnetic substances, which are repelled by magnetic fields.
Transition metals are often paramagnetic due to these unpaired d electrons. For instance, iron and nickel are famous for their magnetic properties, stemming from their unpaired electrons.
Noteworthy points about paramagnetism include:

• It's caused by unpaired electrons reacting to magnetic fields.


• This trait is prevalent among transition metals.


• Magnetic properties are significant in technological applications.