Theory of ionization was given by

Options

A. Rutherford
B. Graham
C. Faraday
D. Arrhenius

Explanation

**Step-by-Step Solution:**

1. **Identify the Scientist**: The question asks for the scientist who proposed the theory of ionization. The correct answer is Svante Arrhenius.

2. **Understanding Ionization**: Arrhenius proposed that acids and bases ionize in water. An acid (HA) dissociates into hydrogen ions (H⁺) and its conjugate base (A⁻) when dissolved in water.

3. **Ionization of a Weak Acid**: For a weak acid (HA), the ionization can be represented as:
\[ HA \rightleftharpoons H^+ + A^- \]
Here, the initial concentration of the acid is denoted as C.

4. **Ionization Constant (Kₐ)**: The ionization constant for the weak acid can be expressed as:
\[ K_a = \frac{[H^+][A^-]}{[HA]} \]
If α is the degree of ionization, then:
\[ [H^+] = C \alpha \quad \text{and} \quad [A^-] = C \alpha \]
The concentration of the undissociated acid is:
\[ [HA] = C(1 - \alpha) \]

5. **Substituting into the Ionization Constant**: Substituting these values into the expression for \( K_a \):
\[ K_a = \frac{(C \alpha)(C \alpha)}{C(1 - \alpha)} = \frac{C \alpha^2}{1 - \alpha} \]

6. **Behavior with Dilution**: According to Arrhenius, as the solution is diluted (more water is added), the degree of ionization (α) increases, leading to a higher concentration of ions in the solution.

7. **Conclusion**: Thus, the theory of ionization was given by Svante Arrhenius, and it describes how acids and bases dissociate into ions in aqueous solutions.