The alkali metal having highest melting point is

Options

A. Li
B. Na
C. Cs
D. Rb

Explanation

To determine which alkali metal has the highest melting point, we can follow these steps:

### Step 1: Understand the Properties of Alkali Metals
Alkali metals are found in Group 1 of the periodic table and include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). They are known for having low melting points compared to other metals.

**Hint:** Remember that alkali metals have large atomic sizes which generally lead to lower melting points.

### Step 2: Compare the Sizes of Alkali Metals
Among the alkali metals, lithium is the smallest in size. As we move down the group from lithium to francium, the size of the atoms increases.

**Hint:** Consider how atomic size affects the strength of metallic bonds in the crystal lattice.

### Step 3: Analyze the Binding Energy
The melting point of a metal is influenced by the strength of the metallic bonds, which is related to the binding energy in the crystal lattice. Smaller atoms can pack more closely together, leading to stronger metallic bonds and higher melting points.

**Hint:** Recall that stronger atomic packing leads to higher binding energy and thus a higher melting point.

### Step 4: Identify Lithium as the Exception
Since lithium is the smallest alkali metal, it has stronger atomic packing compared to the other alkali metals. This results in a higher binding energy in its crystal lattice, making lithium have the highest melting point among the alkali metals.

**Hint:** Think about how the unique properties of lithium set it apart from the other alkali metals.

### Step 5: Conclusion
Based on the analysis, we conclude that lithium (Li) is the alkali metal with the highest melting point.

**Final Answer:** The alkali metal having the highest melting point is lithium (Li).