The correct decreasing order of basic strength of the following species is ….. `H_(2)O, NH_(3), OH^(-),NH_(2)^(-)`

Options

A. `NH_(2)^(-) gt OH^(-) gt NH_(3) gt H_(2)O^(-)`
B. `OH^(-) gt NH_(2)^(-) gt H_(2)O gt NH_(2)^(-)`
C. `NH_(3) gt H_(2)O gt NH_(2)^(-) gt OH^(-)`
D. `H_(2)O gt NH_(3) gt OH^(-) gt NH_(2)^(-)`

Explanation

To determine the correct decreasing order of basic strength of the species \( H_2O \), \( NH_3 \), \( OH^- \), and \( NH_2^- \), we can follow these steps:

### Step 1: Identify the Species
We have four species to consider:
1. Water (\( H_2O \))
2. Ammonia (\( NH_3 \))
3. Hydroxide ion (\( OH^- \))
4. Amide ion (\( NH_2^- \))

### Step 2: Understand Basicity
Basicity refers to the ability of a species to accept protons (H⁺ ions). Generally, negatively charged species are more basic than neutral species because they have an extra electron that can be donated to bond with a proton.

### Step 3: Compare the Negatively Charged Species
Among \( OH^- \) and \( NH_2^- \):
- \( OH^- \) has oxygen as the central atom, while \( NH_2^- \) has nitrogen.
- Oxygen is more electronegative than nitrogen, which means it holds onto its electrons more tightly and is less willing to donate them.
- Therefore, \( NH_2^- \) is more basic than \( OH^- \).

### Step 4: Compare the Neutral Species
Among \( H_2O \) and \( NH_3 \):
- Water has oxygen, and ammonia has nitrogen as the central atom.
- Again, since nitrogen is less electronegative than oxygen, \( NH_3 \) is more basic than \( H_2O \).

### Step 5: Combine the Results
Now we can combine our findings to establish the order of basicity:
1. \( NH_2^- \) (most basic)
2. \( OH^- \)
3. \( NH_3 \)
4. \( H_2O \) (least basic)

### Final Order
Thus, the correct decreasing order of basic strength is:
\[ NH_2^- > OH^- > NH_3 > H_2O \]