A cobalt target `(Z = 27)` is bomberded with electron and the wavelength of its characteristic spectrum are measured . A second , fainter characcteristic spectrum is also found because of an impurity in the target. The wevelength of the `K_(alpha)` lines are 178.9 pm (cobalt) and `143.5 pm` (impurity). What is the impurity?

Explanation

To solve the problem, we need to determine the atomic number of the impurity based on the given wavelengths of the K_alpha lines for cobalt and the impurity. We will use Moseley's law, which relates the frequency of X-ray emission to the atomic number of the element.

### Step-by-Step Solution:

1. **Identify the Given Values**:
- Wavelength of K_alpha for Cobalt (λ_Co) = 178.9 pm
- Wavelength of K_alpha for Impurity (λ_X) = 143.5 pm
- Atomic number of Cobalt (Z_Co) = 27
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