Which of the following is in the lanthanide family?
A) Uranium
B) Promethium
C) Silver
D) Gold
The Correct Answer and Explanation is:
The correct answer is: B) Promethium
Explanation:
The lanthanide family consists of elements in the periodic table from atomic number 57 (lanthanum) to 71 (lutetium). These elements, known as the rare earth metals, belong to the f-block of the periodic table and are characterized by their filling of the 4f orbitals.
Characteristics of Lanthanides:
- Electronic Configuration: The general electron configuration for lanthanides is ( [Xe]4f^{1-14}5d^{0-1}6s^2 ).
- Physical Properties: Lanthanides are silvery-white, soft metals that tarnish when exposed to air. They are also good conductors of electricity.
- Chemical Properties: They are highly reactive, particularly at high temperatures, and tend to form compounds in the +3 oxidation state.
Element Analysis:
- Uranium (A): Uranium (atomic number 92) belongs to the actinide series, not the lanthanides. Actinides occupy the 5f block and include radioactive elements.
- Promethium (B): Promethium (atomic number 61) is a member of the lanthanide series. It is unique because it is one of the two lanthanides that are radioactive (the other being samarium isotopes). It is not found naturally in significant quantities on Earth and is usually synthesized.
- Silver (C): Silver (atomic number 47) is a transition metal and does not belong to the lanthanide series.
- Gold (D): Gold (atomic number 79) is also a transition metal, not a lanthanide.
Importance of Lanthanides:
Lanthanides, including promethium, are critical in many industries. They are used in magnets, catalysts, phosphors for LED lights, and nuclear technology. Promethium specifically has applications in luminous paints and nuclear batteries.
In summary, promethium is the only element in the lanthanide family among the choices provided.