Given below are two statements :
Statement (I) : The 4 f and 5 f - series of elements are placed separately in the Periodic table to preserve the principle of classification.
Statement (II) : S-block elements can be found in pure form in nature.
In the light of the above statements, choose the most appropriate answer from the options given below :

Solution

Chemistry ma’am · 3 steps

Judge each statement alone: why f-blocks sit at the bottom, and how reactive s-block metals are.

1. Statement I. The 14 lanthanoids (4f) and 14 actinoids (5f) behave very much like each other, so each set belongs in one slot of group 3. Writing them as separate rows below the table keeps elements with similar properties in a single column. That is the principle of classification, and it also stops the table from becoming too wide. True.
2. Statement II. s-block elements have only 1 or 2 valence electrons and very low ionisation enthalpies, so they lose them very easily. They react quickly with air and water, so in nature they occur only as compounds such as NaCl, KCl and CaCO₃. False.
3. So. Statement I is true and Statement II is false, which is option (c).

The idea to keep. The f-block rows sit at the bottom so that elements with similar properties share one column. Alkali and alkaline earth metals are far too reactive to occur free in nature.

Answer from the NTA final answer key. Solution by PrepWiser.