Question

Which of the following is not true about s-block elements?
A. They have large atomic size
B. They have lower ionization enthalpies
C. They have variable oxidation state
D. They form basic oxides

Answer 1

Hint: I A and II A Group elements are called s-block elements. They are also called alkali and alkaline earth metals. As moving from left to right in periodic table the metallic character decreases means s-block elements are metallic in nature.

Complete step by step answer:
Group I A and II A are called s-block elements.
Coming to given options, option A, s-block elements have large size. Yes it is true. As we are moving from top to bottom in the periodic table the atomic size increases. Group I A and II A elements have large atomic size when compared to other elements in the periodic table.
Coming to option B, they have lower ionization enthalpies. Yes it is true. Because of the large atomic size we can remove the electrons from the outer shell with a small amount of energy. So, s-block elements have lower ionization enthalpies.
Coming to option C, s-block elements have variable oxidation state. It is wrong. Because s-block elements have only 1 or 2 free electrons to donate. So they exhibit either +1 or +2 oxidation states. So, s-block elements don’t exhibit variable oxidation states.
Coming to option D, s-block elements form basic oxides, yes it is true. All oxide of the s-block elements are basic in nature.
So, the correct option is C, it is not true about s-block elements.

Note: Don’t be confused with the words Group I A and II A and s-block elements.
Group I A and II A are also called as s-block elements and
Group I A –alkali metals.
Group II A –alkaline earth metals.