Which of the following statements is correct for s-block elements?

The correct answer is option 4. All are correct.

Let us delve into each statement regarding s-block elements and explain why they are correct:

1. They are strong reducing agents.

s-block elements, which include alkali metals (Group 1) and alkaline earth metals (Group 2), are strong reducing agents because they have a strong tendency to lose electrons and form positive ions (cations). This characteristic arises from their low ionization energies and the ease with which they can donate electrons. For example, alkali metals like lithium (Li), sodium (Na), and potassium (K) readily donate their single valence electron to form Li⁺, Na⁺, and K⁺ ions, respectively. These ions have a strong reducing potential and can reduce other substances by donating electrons.

2. Their hydroxides are strong bases.

The hydroxides of s-block elements are indeed strong bases. Alkali metals (Group 1) form hydroxides such as lithium hydroxide (LiOH), sodium hydroxide (NaOH), and potassium hydroxide (KOH), which are all strong bases. These hydroxides dissociate completely in water to produce hydroxide ions (\(OH^-\)), leading to a highly alkaline solution. Alkaline earth metals (Group 2) also form strong bases like calcium hydroxide (Ca(OH)\(_2\)), strontium hydroxide (Sr(OH)\(_2\)), and barium hydroxide (Ba(OH)\(_2\)), although they are less soluble compared to alkali metal hydroxides.

3. s-block elements are most reactive of all the metals.

s-block elements, especially alkali metals (Group 1), are indeed among the most reactive metals in the periodic table. This high reactivity stems from their low ionization energies and strong reducing properties. Alkali metals react vigorously with water, oxygen, and halogens. For example, sodium and potassium react explosively with water due to the rapid production of hydrogen gas. Alkaline earth metals (Group 2) are less reactive than alkali metals but are still more reactive than most other metals. They react readily with water and acids, although their reactivity is lower compared to alkali metals.

4. All are correct.

Given the explanations above, all three statements (1, 2, and 3) are correct for s-block elements. They are strong reducing agents due to their ability to donate electrons, their hydroxides are strong bases that dissociate completely in water, and they are among the most reactive metals in the periodic table.

The correct answer, which is (4) All are correct, reflects the accurate characterization of s-block elements based on their properties as reducing agents, bases, and reactive metals. These properties make them distinctive and important in various chemical reactions and applications.