Which among the following is kinetically inert towards water?

Options

A. Na
B. Be
C. Ca
D. K

Explanation

To determine which element is kinetically inert towards water among the given options, we can follow these steps:

### Step 1: Understand the Reactivity of S-Block Elements
The s-block elements include alkali metals (like sodium, potassium) and alkaline earth metals (like calcium, beryllium). These metals typically react with water, but the extent of their reactivity varies.

**Hint:** Review the general reactivity trends of s-block elements with water.

### Step 2: Analyze Each Element
- **Sodium (Na):** Reacts vigorously with water to produce sodium hydroxide and hydrogen gas.
- **Calcium (Ca):** Also reacts with water, though less vigorously than sodium, to form calcium hydroxide and hydrogen gas.
- **Potassium (K):** Reacts explosively with water, producing potassium hydroxide and hydrogen gas.
- **Beryllium (Be):** Does not react with water, even when red hot, due to the formation of a protective oxide layer.

**Hint:** Consider the specific reactions of each metal with water and their reactivity levels.

### Step 3: Identify the Kinetically Inert Element
From the analysis, we see that sodium, calcium, and potassium all react with water. In contrast, beryllium does not react due to its protective oxide layer and high lattice energy, which makes it kinetically inert towards water.

**Hint:** Focus on the protective mechanisms that prevent beryllium from reacting with water.

### Step 4: Conclude the Answer
The element that is kinetically inert towards water is **beryllium (Be)**.

**Final Answer:** Beryllium (option 2) is kinetically inert towards water.