Characteristics of Transition Metals
They are a group of chemical elements found in the periodic table, with atomic numbers ranging from 21 to 30, 39 to 48, and 57 to 80. They are called so because they are located between the main group, and have intermediate properties between those of the main group and those in the lanthanide and actinide series. This article will discuss the characteristics of transition metals.
They have a partially filled d subshell in their electron configuration, so they have unique properties. The d subshell can accommodate up to 10 electrons, and they have between 1 and 10 in this subshell. The partially filled d subshell gives rise to these elements’ characteristic color, magnetism, and paramagnetism.
One of the most striking characteristics of transition metals is their vivid colors. This is due to the presence of unpaired electrons in the d subshell, which can absorb specific wavelengths of visible light and reflect others, giving rise to the characteristic color of the metal. For example, copper (Cu) is reddish-brown, while nickel (Ni) is silver-white. The ligands surrounding the metal ion also influence the color complexes.
They exhibit different degrees of magnetism, depending on the number of unpaired electrons in their d subshell. This gives rise to magnetic moments, which can be aligned in a magnetic field, leading to magnetization. Iron (Fe), cobalt (Co), and nickel (Ni) are ferromagnetic, meaning that they are strongly magnetized in the presence of a magnetic field. Manganese (Mn) and chromium (Cr) are antiferromagnetic, meaning their magnetic moments are aligned in opposite directions, leading to no net magnetization. Others, such as copper (Cu) and zinc (Zn) are diamagnetic, meaning they are not magnetized in a magnetic field.
The oxidation states are important in their reactivity and chemical properties. Transition metals essentially exhibit a wide range of oxidation states due to their ability to lose or gain electrons from the d subshell. The oxidation states range from +1 to +7, the most common being +2 and +3. For example, iron (Fe) can exist in the +2 or +3 oxidation state, while copper (Cu) can exist in the +1 or +2 oxidation state.
They strongly tend to form coordination complexes, in which a group of ligands surrounds a central metal ion. The ligands are usually molecules or ions with one or more unshared pairs of electrons, which can coordinate with the metal ion. The coordination complexes of transition metals have a wide range of applications, such as in catalysis, medicine, and materials science.
The catalytic activity is due to their ability to change their oxidation state and form intermediates that promote the reaction. Their ability to form coordination complexes with ligands allows them to act as efficient catalysts in various reactions. For example, platinum (Pt) is used as a catalyst in the production of nitric acid. In contrast, iron (Fe) is used as a catalyst in the Haber process to produce ammonia.
High melting and boiling points
They essentially have high melting and boiling points due to the strength of the metallic bond between the atoms. The sharing of valence electrons forms the metallic bond; in this case, the d electrons also contribute to the bonding. The high melting and boiling points make them useful in high-temperature applications, such as in the production of alloys and in aerospace and nuclear industries.
Another important characteristic of transition metals is their crystal structure, which can be different from other metals. Many have a body-centered cubic (bcc) crystal structure, which is a type of crystal lattice where the atoms are arranged in a cube, with an atom in the center of the cube and one at each corner. This unique structure contributes to their mechanical properties and makes them useful in applications such as construction and engineering.
Transition metals are generally very dense. The density of a metal is determined by the mass of its atoms and the spacing of those atoms in a crystal lattice. The d electrons play a significant role in the density of these metals, as they can contribute to both the metallic bonding and the crystal structure. For example, tungsten (W) is one of the densest metals, with a density of 19.3 g/cm³.
Many transition metals are highly resistant to corrosion. This is due to the formation of a thin layer of oxide on the metal’s surface, which acts as a barrier to further corrosion. This oxide layer is stable and adheres strongly to the metal surface, preventing the metal from reacting with its environment. For example, titanium (Ti) is highly corrosion-resistant and is used in aircraft, spacecraft, and medical implants.
Some of the transition metals in the periodic table are radioactive. This means that their nuclei are unstable and can undergo radioactive decay, emitting radiation in the process. The radioactive transition metals include technetium (Tc), promethium (Pm), and all the elements with atomic numbers higher than 83, which are the actinides. These elements have many important applications in nuclear power, nuclear medicine, and scientific research.
Transition metals play essential roles in many biological processes. They are found in enzymes and proteins that perform critical functions, such as photosynthesis, respiration, and DNA synthesis. Iron (Fe) is necessary for the production of hemoglobin, the protein that carries oxygen in the blood. Copper (Cu) is needed for the synthesis of connective tissue and the formation of red blood cells.
In conclusion, transition metals are a unique group of elements with partially filled d subshells in their electron configurations, giving rise to their distinctive properties. These properties include vivid colors, various degrees of magnetism, a wide range of oxidation states, and the ability to form coordination complexes, which contribute to their applications in catalysis, medicine, and materials science. Their high melting and boiling points, crystal structures, density, and resistance to corrosion make them useful in high-temperature applications and engineering. Additionally, many transition metals are radioactive and play essential roles in biological processes, demonstrating their importance in various fields of study.