A, B, C and D are four elements with atomic numbers Z - 1, Z, Z + 1 and Z + 2 respectively. B is a noble gas. Predict
which element exists +2 oxidation state.

Explanation

To determine which element among A, B, C, and D exists in the +2 oxidation state, we will analyze the information given in the question step by step.

### Step 1: Identify the elements and their atomic numbers
- We have four elements:
- A: Atomic number \( Z - 1 \)
- B: Atomic number \( Z \) (given as a noble gas)
- C: Atomic number \( Z + 1 \)
- D: Atomic number \( Z + 2 \)
...