Animated Solution for Chemistry - s and p-Block Elements: Match List-I with List-II. $\begin{array}{ll}\text{List-I}& \text{List-II}\\ \text{A. NaOH}& \text{I. Acidic}\\ {\text{B. Be(OH)}}_2& \text{II. Basic}\\ {\text{C. Ca(OH)}}_2& \text{III. Amphoteric}\\ {\text{D. B(OH)}}_3& \\ {\text{E. Al(OH)}}_3& \end{array}$ Choose the most appropriate answer from the options given below.

A Map of Chemical Personalities

Look closely at the periodic table. The position of an element tells us a lot about its chemical behavior. As a general rule, s-block elements are strong metals, so they form basic hydroxides. Non-metals form acidic hydroxides. And elements sitting on the fence? They form amphoteric hydroxides, meaning they can act as both acids and bases.

Sodium and Calcium

Let's start with Sodium ($\text{Na}$) and Calcium ($\text{Ca}$). Sodium is a Group 1 alkali metal, and Calcium is a Group 2 alkaline earth metal. Both are highly electropositive. Because they easily give up electrons, the oxygen in their hydroxide groups holds tightly to the hydrogen, making it very easy for the entire ${\text{OH}}^{-}$ ion to detach in water.

So, their hydroxides, $\text{NaOH}$ and ${\text{Ca(OH)}}_2$, are definitely basic in nature.

Boron

Now, look at Boron ($\text{B}$) in Group 13. Boron is a non-metal. When it forms a hydroxide, ${\text{B(OH)}}_3$, it actually behaves as an acid.

In fact, you might know it better as Boric acid, often written as ${\text{H}}_3{\text{BO}}_3$. Because Boron is electron-deficient, it doesn't release ${\text{OH}}^{-}$ ions. Instead, it accepts an ${\text{OH}}^{-}$ ion from a water molecule, which forces the water to release an ${\text{H}}^{+}$ ion. So, Boron hydroxide is strictly acidic.

Beryllium and Aluminum

There is a catch here. Beryllium ($\text{Be}$) and Aluminum ($\text{Al}$). Even though Beryllium is in Group 2, it's very small and has an exceptionally high polarizing power.

It shares a diagonal relationship with Aluminum in Group 13. Because of this high charge density, the bonds they form with oxygen have significant covalent character. This allows the molecule to break in two different ways depending on the environment. Because of this, both ${\text{Be(OH)}}_2$ and ${\text{Al(OH)}}_3$ are amphoteric. They can react with both acids and bases.

Let's put it all together and match our lists: - $\text{NaOH}$ is Basic. - ${\text{Be(OH)}}_2$ is Amphoteric. - ${\text{Ca(OH)}}_2$ is Basic. - ${\text{B(OH)}}_3$ is Acidic. - ${\text{Al(OH)}}_3$ is Amphoteric.

Matching these up gives us the correct sequence: $\text{A}\to \text{II}$, $\text{B}\to \text{III}$, $\text{C}\to \text{II}$, $\text{D}\to \text{I}$, $\text{E}\to \text{III}$. Option (b) is our perfect match!