Select the correct order of basic strength?

Options

A. `KOHgtMg(OH)_(2)gtAl(OH)_(3)`
B. `Al(OH)_(3)gtMg(OH)_(2)gtKOH`
C. `Mg(OH)_(2)gtKOHgtAl(OH)_(3)`
D. `KOHgtAl(OH)_(3)gtMg(OH)_(2)`

Explanation

To determine the correct order of basic strength among Potassium Hydroxide (KOH), Magnesium Hydroxide (Mg(OH)₂), and Aluminium Hydroxide (Al(OH)₃), we need to consider the trends in basic strength across periods and down groups in the periodic table.

### Step-by-Step Solution:

1. **Understanding Basic Strength**: Basic strength refers to the ability of a compound to accept protons (H⁺ ions) or donate electron pairs. In the context of hydroxides, stronger bases will dissociate more completely in water to produce hydroxide ions (OH⁻).

2. **Trends Across the Period**: As we move across a period from left to right, the atomic size decreases. This decrease in size leads to an increase in the effective nuclear charge experienced by the valence electrons, making it harder for the atom to lose electrons. Consequently, the basic strength decreases across a period.

3. **Trends Down the Group**: As we move down a group in the periodic table, the atomic size increases due to the addition of electron shells. This increase in size results in a decrease in the effective nuclear charge felt by the outermost electrons, making it easier for these atoms to lose electrons. Therefore, basic strength increases down a group.

4. **Identifying the Elements**:
- Potassium (K) is in Group 1.
- Magnesium (Mg) is in Group 2.
- Aluminium (Al) is in Group 13.

5. **Comparing Basic Strength**:
- **Potassium Hydroxide (KOH)**: Being from Group 1, KOH is expected to be a strong base due to the low ionization energy of potassium.
- **Magnesium Hydroxide (Mg(OH)₂)**: As a Group 2 hydroxide, it is also a strong base, but generally less so than Group 1 hydroxides.
- **Aluminium Hydroxide (Al(OH)₃)**: This is a weaker base compared to both KOH and Mg(OH)₂ due to the higher charge density of Al³⁺, which tends to hydrolyze and form Al(OH)₄⁻ in solution.

6. **Establishing the Order**: Based on the trends and comparisons:
- KOH > Mg(OH)₂ > Al(OH)₃

Thus, the correct order of basic strength is:
**KOH > Mg(OH)₂ > Al(OH)₃**

### Final Answer:
The correct order of basic strength is:
**Potassium Hydroxide (KOH) > Magnesium Hydroxide (Mg(OH)₂) > Aluminium Hydroxide (Al(OH)₃)**