Which of the following is a lanthanide?A.Europium (Eu)B.Gold (Au)C.Barium (Ba)D.Americium (Am)

To determine which of the given options is a lanthanide, we need to briefly explore the properties of lanthanide elements.

Lanthanides Overview

1. Definition: The lanthanides are a series of 15 chemical elements that follow lanthanum (La) in the periodic table, with atomic numbers ranging from 57 (Lanthanum) to 71 (Lutetium).
2. Characteristics: These elements are known for their similar properties, including their reactivity and their ability to form complex ions.

Options Analysis

1. A. Europium (Eu): This element has the atomic number 63, making it a lanthanide.
2. B. Gold (Au): Gold has the atomic number 79 and is categorized as a transition metal.
3. C. Barium (Ba): Barium, with atomic number 56, is an alkaline earth metal, not a lanthanide.
4. D. Americium (Am): Americium has the atomic number 95 and is classified as an actinide, not a lanthanide.

Conclusion

Based on the classification of the elements:

• Europium (Eu) is the only lanthanide among the given options.

Final Answer

A. Europium (Eu) is a lanthanide.