To determine the unknown metal, we first need to calculate its density using the given mass and volume. The formula for density (\( \rho \)) is:
\[ \rho = \frac{\text{mass}}{\text{volume}} \]
For the unknown metal:
- Mass = 428 grams
- Volume = 20 cm³
Now, we calculate the density:
\[ \rho = \frac{428 , \text{g}}{20 , \text{cm}^3} = 21.4 , \text{g/cm}^3 \]
Now we can compare this calculated density with the densities of the metals provided in the table:
- Cobalt: 8.9 g/cm³
- Silver: 10.5 g/cm³
- Lead: 7.2 g/cm³
- Platinum: 11.3 g/cm³
- Chromium: 21.4 g/cm³
The calculated density of the unknown metal is 21.4 g/cm³, which matches the density of Chromium.
Thus, the metal is Chromium.