Which of the following elements has the strongest tendency to form electrovalent compound ?

Options

A. Li
B. Na
C. Be
D. Mg

Answer

To determine which of the following elements has the strongest tendency to form an electrovalent (ionic) compound, we need to analyze the options provided: Lithium (Li), Sodium (Na), Beryllium (Be), and Magnesium (Mg).

### Step 1: Understanding Electrovalent Compounds
Electrovalent compounds are formed when there is a transfer of electrons from one atom to another, resulting in the formation of cations and anions. The tendency to form such compounds is influenced by the charge on the cation and the size of the cation.

**Hint:** Remember that cations are positively charged ions formed by losing electrons.

### Step 2: Identifying the Cations
We can convert the elements into their respective cations:
- Lithium (Li) → Li⁺ (charge +1)
- Sodium (Na) → Na⁺ (charge +1)
- Beryllium (Be) → Be²⁺ (charge +2)
- Magnesium (Mg) → Mg²⁺ (charge +2)

**Hint:** Look at the charges of the cations; higher positive charge usually indicates a stronger tendency to form ionic bonds.

### Step 3: Analyzing Ionic Character
According to Fajans’ rules, the ionic character of a compound is directly proportional to the size of the cation and inversely proportional to the charge on the cation. This means:
- Cations with a lower charge and larger size will have a greater tendency to form ionic compounds.

**Hint:** Larger cations with lower charges are more likely to exhibit ionic character.

### Step 4: Comparing Sizes of Cations
- Lithium ion (Li⁺) and Sodium ion (Na⁺) belong to Group 1 (alkali metals).
- Beryllium ion (Be²⁺) and Magnesium ion (Mg²⁺) belong to Group 2 (alkaline earth metals).

In general, as we move down a group, the size of the cation increases due to the addition of electron shells. Therefore:
- Na⁺ is larger than Li⁺.
- Mg²⁺ is smaller than Be²⁺.

**Hint:** Remember that atomic size increases down a group and decreases across a period.

### Step 5: Conclusion
Since Na⁺ has a +1 charge and is larger than Li⁺, it will have a stronger tendency to form electrovalent compounds compared to Li⁺. On the other hand, Be²⁺ and Mg²⁺ have a +2 charge, which makes them less favorable for forming ionic compounds compared to Na⁺.

Thus, the element with the strongest tendency to form an electrovalent compound among the given options is **Sodium (Na)**.

**Final Answer:** Sodium (Na)