The valence shell of an element `""_(20)^(40)X` is the 3rd shell.

Explanation

To determine whether the statement about the valence shell of the element \( _{20}^{40}X \) is true or false, we need to analyze the electronic configuration of the element with atomic number 20.

### Step-by-Step Solution:

1. **Identify the Atomic Number and Mass Number**:
- The atomic number of the element \( X \) is 20, which indicates that it has 20 electrons.
- The mass number is 40, but for determining the valence shell, we focus on the atomic number.

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