Which of the following is the strongest base ?

Options

A. `Dyl(OH)_3`
B. `La(OH)_3`
C. `Lu(OH)_3`
D. `Yb(OH)_3 `

Explanation

To determine which of the following compounds is the strongest base among Dysprosium hydroxide (Dy(OH)₃), Lanthanum hydroxide (La(OH)₃), Lutetium hydroxide (Lu(OH)₃), and Ytterbium hydroxide (Yb(OH)₃), we can follow these steps:

### Step 1: Understand the Concept of Basicity
Basicity refers to the ability of a compound to accept protons (H⁺ ions) or donate hydroxide ions (OH⁻). In the case of metal hydroxides, the stronger the base, the more readily it can release OH⁻ ions in solution.

### Step 2: Identify the Elements
The given compounds are hydroxides of lanthanide elements:
- Dysprosium (Dy) - Atomic number 66
- Lanthanum (La) - Atomic number 57
- Lutetium (Lu) - Atomic number 71
- Ytterbium (Yb) - Atomic number 70

### Step 3: Consider the Lanthanide Contraction
As we move across the lanthanide series from Lanthanum to Lutetium, the atomic size decreases due to lanthanide contraction. This contraction occurs because of the poor shielding effect of the 4f electrons, leading to a stronger effective nuclear charge experienced by the outer electrons.

### Step 4: Analyze the Size and Basicity Relationship
In general, larger metal cations tend to form stronger bases because they can stabilize the negative charge of the hydroxide ion better. Therefore, the order of size (and thus basicity) among these hydroxides will be inversely related to their atomic numbers:
- La(OH)₃ > Dy(OH)₃ > Yb(OH)₃ > Lu(OH)₃

### Step 5: Determine the Strongest Base
From the analysis, Lanthanum hydroxide (La(OH)₃) will be the strongest base because it has the largest ionic size among the given options. Therefore, it can better stabilize the hydroxide ions compared to the others.

### Conclusion
The strongest base among the given options is **Lanthanum hydroxide (La(OH)₃)**, which corresponds to option B.