An ion `X^(2-)` contains 10 electrons and 8 neutrons. The atomic number of the element X is

Explanation

To determine the atomic number of the element \( X \) from the ion \( X^{2-} \) which contains 10 electrons and 8 neutrons, we can follow these steps:

### Step 1: Understand the Ion
The ion \( X^{2-} \) indicates that it has a negative charge of 2. This means that the ion has gained 2 additional electrons compared to its neutral state.

### Step 2: Determine the Number of Electrons in the Neutral Atom
Since the ion has 10 electrons, and it is a \( 2- \) ion, we can find the number of electrons in the neutral atom \( X \) by subtracting the 2 extra electrons gained:
\[ \text{Electrons in neutral atom} = \text{Electrons in ion} - 2 = 10 - 2 = 8 \]

### Step 3: Relate Electrons to Atomic Number
The atomic number \( Z \) of an element is defined as the number of protons in the nucleus, and in a neutral atom, the number of protons is equal to the number of electrons. Therefore, for the neutral atom \( X \):
\[ Z = \text{Number of electrons in neutral atom} = 8 \]

### Step 4: Conclusion
Thus, the atomic number of the element \( X \) is 8.

### Final Answer
The atomic number of the element \( X \) is **8**.

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