Final answer:
Second generation metals typically refer to transition metals with incomplete d sub-levels, which display properties such as multiple oxidation states, the ability to form colorful compounds, and are useful as catalysts in chemical reactions.
Step-by-step explanation:
The term '2nd generation metals' often refers to the metals found in the second block (Groups 3 to 12) of the periodic table, known as the transition metals. These metals are characterized by the presence of an incomplete d sub-level in one or more of their common oxidation states. Transition metals are recognized for their ability to form colorful compounds, variable oxidation states, and their use as catalysts in various chemical reactions. For instance, iron (Fe), a well-known second-generation metal, can exist in a +2 or +3 oxidation state and is integral to the synthesis of steel.
Another example is copper (Cu), which is essential in the manufacturing of electrical wires due to its high electrical conductivity. Cu typically exists in a +1 or +2 oxidation state. The physical properties of these metals can significantly vary; they generally possess a high melting point, great strength, and high density. These characteristics of transition metals are important in a wide range of industrial applications and technologies.