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.
  Element Y will have following property: 

Options

A. Atomic number of Y is higher than atomic number of Z.
B. Atomic number of Y is higher than atomic number of X.
C. Element Y is placed in periodic table at left side of element X if both are in same period.
D. None of these

Answer

To solve the question regarding the properties of element Y, we can follow these steps:

### Step 1: Identify the Elements
We know that X, Y, and Z are consecutive elements. Let's denote:
- X = Fluorine (F)
- Y = Oxygen (O)
- Z = Neon (Ne)

### Step 2: Determine the Isoelectronic Condition
According to the question, when X (Fluorine) gains one electron, and Y (Oxygen) gains two electrons, both become isoelectronic with Z (Neon).

- Fluorine (F) has an atomic number of 9. When it gains one electron, it becomes F⁻ with an atomic number of 10, which is isoelectronic with Neon (Ne).
- Oxygen (O) has an atomic number of 8. When it gains two electrons, it becomes O²⁻ with an atomic number of 10, which is also isoelectronic with Neon (Ne).

### Step 3: Analyze the Atomic Numbers
- Atomic number of X (Fluorine) = 9
- Atomic number of Y (Oxygen) = 8
- Atomic number of Z (Neon) = 10

### Step 4: Evaluate the Properties of Element Y
Now, we need to evaluate the properties of element Y (Oxygen) based on its position in the periodic table:
1. **Atomic number of Y is higher than atomic number of Z**: This is false because Y (Oxygen) has an atomic number of 8, which is less than Z (Neon) with an atomic number of 10.
2. **Atomic number of Y is higher than atomic number of X**: This is false because Y (Oxygen) has an atomic number of 8, which is less than X (Fluorine) with an atomic number of 9.
3. **Element Y is placed in the periodic table at the left side of element X if both are in the same period**: This is true because in the periodic table, Oxygen (Y) is to the left of Fluorine (X) in the same period (2nd period).

### Conclusion
Based on the analysis, the correct property of element Y is that it is placed in the periodic table at the left side of element X (Fluorine).

### Final Answer
Element Y will have the property that it is placed in the periodic table at the left side of element X if both are in the same period.

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