Among the lanthanides, the one obtained by synthetic method is
- Lu
- Pm
- Pr
- Gd
The Correct Option is B
Approach Solution - 1
Correct answer: Promethium
Promethium (Pm), atomic number 61, is the only lanthanoid that is radioactive.
Key points:
- All isotopes of Promethium are unstable and exhibit radioactivity.
- It does not occur naturally in significant amounts on Earth and is typically produced in nuclear reactors.
- Other lanthanoids such as Lanthanum, Praseodymium, and Cerium are stable or have stable isotopes.
Approach Solution -2
The only lanthanoid which is radioactive is Promethium.
Explanation:
- Promethium (Pm) is a synthetic element and all its isotopes are radioactive.
- The other lanthanoids listed (Lanthanum, Praseodymium, and Cerium) have stable isotopes and are not radioactive.
Therefore, the correct answer is:
Promethium
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Concepts Used:
D and F Block Elements
The d-block elements are placed in groups 3-12 and F-block elements with 4f and 5f orbital filled progressively. The general electronic configuration of d block elements and f- block elements are (n-1) d 1-10 ns 1-2 and (n-2) f 1-14 (n-1) d1 ns2 respectively. They are commonly known as transition elements because they exhibit multiple oxidation states because of the d-d transition which is possible by the availability of vacant d orbitals in these elements.
They have variable Oxidation States as well as are good catalysts because they provide a large surface area for the absorption of reaction. They show variable oxidation states to form intermediate with reactants easily. They are mostly lanthanoids and show lanthanoid contraction. Since differentiating electrons enter in an anti-penultimate f subshell. Therefore, these elements are also called inner transition elements.
Read More: The d and f block elements