Question

Rare-earth elements are exhibited by_______.

• A. Atomic numbers $21\mathrm{to}30$
• B. Atomic numbers $39\mathrm{to}71$
• C. Atomic numbers $58\mathrm{to}71$
• D. Atomic numbers $81\mathrm{to}91$

Answer 1

The correct option is C

Atomic numbers $58\mathrm{to}71$

Explanation for correct answer:-

Option: (C)

• Rare earth elements are also known as the Lanthanide series which is a part of the f-block of the modern periodic table.
• The Lanthanide Series contains elements from atomic numbers $58-71.$
• Rare earth elements are basically the elements present in the top extended row placed below the main body of the periodic table which is stretched from Cerium (Ce) to Lutetium (Lu).
• A total of 15 elements are grouped under this block.
• These elements are not found on earth's crust and are formed during nuclear reactions and are formed in certain mineral rocks.

Explanation for incorrect answer:-

Options: (A)

• The elements with atomic numbers 21-30 are a member of the d-block.
• These elements constitute the whole 3d-series in the d-block of the modern periodic table.

Option: (B)

• These elements constitute a variety of elements starting from the members of the 4d-series elements and the Lanthanide series.
• The range of tomic numbers from 39 to 71 have rare earth elements but not all elements in that atomic no range are not considered rare earth elements.

Option: (D)

• Elements that are included in the given range of atomic numbers $81\mathrm{to}91$81 to 91are not considered rare earth elements.
• The elements that are included in this range of atomic numbers are elements from p-block such as Thallium and elements from the f-block elements.