Which one of the following alkali metals is the most metallic?

Options

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

Answer

To determine which alkali metal is the most metallic among lithium, sodium, potassium, and cesium, we can follow these steps:

### Step 1: Understand Metallic Character
Metallic character refers to the tendency of an element to lose electrons and form positive ions. The more metallic an element is, the more readily it can lose its outermost electron.

**Hint:** Remember that metallic character is linked to reactivity, especially in alkali metals.

### Step 2: Consider the Group Trend
In the periodic table, alkali metals are located in Group 1. As you move down the group from lithium (Li) to cesium (Cs), the atomic size increases due to the addition of electron shells.

**Hint:** Think about how the size of the atom affects the attraction between the nucleus and the outermost electron.

### Step 3: Analyze Atomic Size and Ionization Energy
As the atomic size increases, the distance between the nucleus and the outermost electron also increases. This leads to a weaker attraction between the nucleus and the outermost electron, making it easier for the atom to lose that electron.

**Hint:** Recall that a larger atomic size generally correlates with lower ionization energy.

### Step 4: Compare the Alkali Metals
- **Lithium (Li)**: Smallest size, highest ionization energy, least metallic character.
- **Sodium (Na)**: Larger than lithium, lower ionization energy, more metallic than lithium.
- **Potassium (K)**: Larger than sodium, lower ionization energy, more metallic than sodium.
- **Cesium (Cs)**: Largest size, lowest ionization energy, most metallic character.

**Hint:** Identify which alkali metal has the largest atomic size and the lowest ionization energy.

### Step 5: Conclusion
Since cesium has the largest atomic size and the lowest ionization energy among the options provided, it is the most metallic alkali metal.

**Final Answer:** Cesium (Cs) is the most metallic alkali metal.