The nucleus of a gaseous element is represented as `""_(y)^(2y)X`. This gas is used in weather observation balloons. Identify the element.

Explanation

To solve the problem, we need to analyze the information given about the gaseous element represented as `""_(y)^(2y)X`.

### Step-by-Step Solution:

1. **Understanding the Notation**: The notation `""_(y)^(2y)X` indicates that:
- `y` is the atomic number of the element.
- `2y` is the atomic mass of the element.
- `X` represents the symbol of the element.
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