X, Y and Z are three consecutive elements. X on addition of one electron and Y on addition of two electrons become isoelectronic with element Z.
Select correct statement: 

Options

A. Difference between atomic number of X and Y is 3.
B. Difference between total number of protons of X and Y is 2.
C. Both (A) and (B).
D. Difference between atomic number of X and Z is 1.

Answer

To solve the problem step by step, we need to analyze the given information about the elements X, Y, and Z.

### Step 1: Understand the Problem
We have three consecutive elements: X, Y, and Z. The problem states that:
- Element X becomes isoelectronic with Z when it gains one electron.
- Element Y becomes isoelectronic with Z when it gains two electrons.

### Step 2: Define Isoelectronic Species
Isoelectronic species are atoms or ions that have the same number of electrons. Therefore, we need to find elements X, Y, and Z such that:
- X + 1 electron = Z
- Y + 2 electrons = Z

### Step 3: Identify Possible Elements
Let’s assume:
- Z is an element with atomic number \( Z \).
- X has atomic number \( Z - 1 \) (since it gains one electron to become isoelectronic with Z).
- Y has atomic number \( Z - 2 \) (since it gains two electrons to become isoelectronic with Z).

### Step 4: Choose Specific Elements
To illustrate, let's consider the elements:
- Z = Neon (Ne), atomic number 10.
- Then, X = Fluorine (F), atomic number 9.
- Y = Oxygen (O), atomic number 8.

### Step 5: Verify the Conditions
1. **For X (Fluorine)**:
- Atomic number = 9
- Gains 1 electron → 9 + 1 = 10 (which is the atomic number of Neon).
- Therefore, X (F) + 1 electron = Z (Ne).

2. **For Y (Oxygen)**:
- Atomic number = 8
- Gains 2 electrons → 8 + 2 = 10 (which is the atomic number of Neon).
- Therefore, Y (O) + 2 electrons = Z (Ne).

### Step 6: Analyze the Statements
Now we need to evaluate the statements given in the question:
1. **Difference between atomic number of X and Y is 3.**
- Atomic number of X (F) = 9, Y (O) = 8.
- Difference = 9 - 8 = 1. (This statement is false.)

2. **Difference between total number of protons of X and Y is 2.**
- Protons in X (F) = 9, Protons in Y (O) = 8.
- Difference = 9 - 8 = 1. (This statement is false.)

3. **Both A and B are wrong.**
- Since both statements A and B are false, this statement is true.

4. **Difference between atomic number of X and Z is 1.**
- Atomic number of X (F) = 9, Z (Ne) = 10.
- Difference = 10 - 9 = 1. (This statement is true.)

### Conclusion
The correct statement is:
- The difference between atomic number of X and Z is 1.

### Final Answer
The correct option is **4.**

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