In the second period of periodic table, the ionisation potential of elements increases from left to right because of

Options

A. increase in densities
B. decreases in chemical reactivities
C. decreases in atomic size
D. decreases in electronegativities

Answer

To solve the question regarding why the ionization potential of elements in the second period of the periodic table increases from left to right, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Ionization Potential**:
- Ionization potential (or ionization energy) is defined as the energy required to remove an electron from the outermost shell of a gaseous atom.

2. **Identifying the Elements in the Second Period**:
- The elements in the second period of the periodic table include Lithium (Li), Beryllium (Be), Boron (B), Carbon (C), Nitrogen (N), Oxygen (O), Fluorine (F), and Neon (Ne).

3. **Observing the Trend**:
- As we move from left to right across the second period, we note that the ionization potential increases.

4. **Analyzing Atomic Size**:
- One key factor influencing ionization potential is atomic size. As you move from left to right in a period, the atomic size decreases due to the increasing nuclear charge (more protons in the nucleus) which pulls the electrons closer to the nucleus.

5. **Effect of Decreased Atomic Size**:
- With a smaller atomic size, the outermost electrons are held more tightly by the nucleus. This increased attraction makes it more difficult to remove an electron, thus requiring more energy (higher ionization potential).

6. **Conclusion**:
- Therefore, the increase in ionization potential from left to right in the second period is primarily due to the decrease in atomic size, leading to a stronger attraction between the nucleus and the outermost electrons.

### Final Answer:
The ionization potential of elements in the second period of the periodic table increases from left to right because of the decrease in atomic size.