Which among the following elements have lowest value of `IE_1`?

Options

A. Pb
B. Sn
C. S
D. C

Explanation

To determine which among the given elements has the lowest value of first ionization energy (IE1), we can follow these steps:

### Step 1: Understand Ionization Energy
Ionization energy is the energy required to remove an electron from an atom in its gaseous state. The first ionization energy (IE1) refers specifically to the energy needed to remove the outermost electron.

### Step 2: Identify the Elements
Let's consider the elements mentioned in the video transcript: Carbon (C), Tin (Sn), Lead (Pb), Sulfur (S), and Oxygen (O).

### Step 3: Determine the Electronic Configurations
We need to find the electronic configurations of these elements to understand their outermost electrons:
- **Carbon (C)**: 1s² 2s² 2p²
- **Oxygen (O)**: 1s² 2s² 2p⁴
- **Sulfur (S)**: 1s² 2s² 2p⁶ 3s² 3p⁴
- **Tin (Sn)**: [Kr] 5s² 4d¹⁰ 5p²
- **Lead (Pb)**: [Xe] 6s² 4f¹⁴ 5d¹⁰ 6p²

### Step 4: Analyze the Position in the Periodic Table
- **Carbon** is in Group 14 and Period 2.
- **Oxygen** is in Group 16 and Period 2.
- **Sulfur** is in Group 16 and Period 3.
- **Tin** is in Group 14 and Period 5.
- **Lead** is in Group 14 and Period 6.

### Step 5: Compare the Ionization Energies
Ionization energy generally decreases down a group and increases across a period. Therefore:
- **Carbon** has a relatively high IE1 due to its position in Period 2.
- **Oxygen** has a high IE1 as well, but slightly lower than Carbon.
- **Sulfur** has a lower IE1 than Oxygen because it is in a higher period (Period 3).
- **Tin** and **Lead** will have significantly lower IE1 values due to being in higher periods (5 and 6, respectively).

### Step 6: Conclusion
Among these elements, **Lead (Pb)** will have the lowest first ionization energy (IE1) because it is the heaviest element in the list and is located in a lower period, where ionization energies are generally lower.

### Final Answer
**Lead (Pb) has the lowest value of IE1 among the given elements.**

---