SSC CGL 2022 PYQ — Question 42

The correct answer is Option 2 i.e. Lanthanides.

The 15 naturally occurring metallic chemical elements known as lanthanides have atomic numbers ranging from 57 for lanthanum to 71 for lutetium.

1. (4fx 5d1 6s2) electron configurations are present in them. Since each extra electron is added to a lower-lying 4f orbital, not the valence shell, the lanthanides are all extremely similar chemically.  Although different oxidation states are known, the majority of these elements are reactive, lustrous, silvery-white metals that are typically found in compounds in the +3 oxidation state (from losing the 5d1 6s2 electrons).
2. Due to their molecular similarities, obtaining the lanthanides in their pure metallic state is frequently quite challenging (and expensive).  
3. The lanthanide phosphate salts (Ce, La, Th, Nd, Y)PO4 and the carbonate and fluoride salts ((Ce, La, Y)CO3F, [(Ce, La, Nd)CO3(OH,F)]) found in bastnasite and hydroxyl bastnasite are where they are most commonly found.
4. The lanthanides are frequently employed in a mixture known as misch metal (German for "mixed metal"), which is made up of 50% cerium, 25% lanthanum, and the remaining 25% of a mixture of the remaining lanthanides. Some steels are hardened using this alloy, which is also used to make lighter flints and as a "getter" in vacuums to react with and expel trace gases.