Which among the following elements have the lowest value of `IE_(1)`?

Options

A. Pb
B. Sn
C. Si
D. C

Answer

To determine which element among the carbon family has the lowest first ionization energy (IE₁), we can follow these steps:

### Step 1: Identify the Elements
The elements in the carbon family (Group 14) are:
- Carbon (C)
- Silicon (Si)
- Tin (Sn)
- Lead (Pb)

### Step 2: Understand Ionization Energy Trend
Ionization energy generally decreases as we move down a group in the periodic table. This is because:
- The atomic size increases due to the addition of electron shells.
- The outermost electrons are further from the nucleus and are less tightly held, making them easier to remove.

### Step 3: Analyze the Elements
Based on the trend:
- Carbon (C) has the highest ionization energy.
- Silicon (Si) has a lower ionization energy than carbon.
- Tin (Sn) has a lower ionization energy than silicon.
- Lead (Pb) is expected to have the lowest ionization energy due to its position at the bottom of the group.

### Step 4: Consider Exceptions
However, we must consider the effect of electron shielding and the presence of f-orbitals:
- Lead has 4f electrons, which can cause a contraction in size due to poor shielding (known as lanthanide contraction).
- This contraction can result in lead having a slightly smaller size than tin, which can affect the ionization energy.

### Step 5: Establish the Final Order
After considering the above factors, the order of ionization energy from highest to lowest is:
- Carbon (C) > Silicon (Si) > Lead (Pb) > Tin (Sn)

### Conclusion
Thus, the element with the lowest first ionization energy (IE₁) among the given options is **Tin (Sn)**.

### Final Answer
**Tin (Sn)** has the lowest value of IE₁.

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