Ionization energy is influenced by :

Options

A. Size of the atom
B. Charge on the nucleus
C. Electrons present in inner shells
D. None of the above

Answer

### Step-by-Step Solution:

1. **Understanding Ionization Energy**:
- Ionization energy is defined as the minimum amount of energy required to remove an electron from an atom in its gaseous state.

2. **Factor 1: Size of Atom**:
- The size of the atom affects ionization energy. As the atomic size increases, the distance between the outermost electrons and the nucleus also increases.
- This increased distance results in a decrease in the attractive force between the nucleus and the outer electrons.
- Therefore, as the atomic size increases, the ionization energy decreases.

3. **Factor 2: Charge on the Nucleus (Nuclear Charge)**:
- The nuclear charge refers to the total charge of the nucleus due to the protons present.
- As the nuclear charge increases, the attractive force on the outer electrons increases, making it harder to remove an electron.
- Consequently, an increase in nuclear charge leads to an increase in ionization energy.

4. **Factor 3: Electrons Present in Inner Shells (Shielding Effect)**:
- The electrons in the inner shells can shield the outer electrons from the full effect of the nuclear charge.
- As the shielding effect increases (more inner shell electrons), the effective nuclear charge experienced by the outer electrons decreases.
- This results in a decrease in ionization energy because the outer electrons are held less tightly by the nucleus.

5. **Conclusion**:
- All three factors—size of the atom, charge on the nucleus, and electrons present in inner shells—affect ionization energy.
- Therefore, the correct answer is that all three factors influence ionization energy.