Write the electron configurations of silicon (Z = 14), vanadium (Z = 23) and manganese (Z = 25)…

Step 1. Silicon. $[\text{Ne}]\,3s^2 3p^2$: two single $3p$ electrons, so $2$ unpaired.

Step 2. Vanadium. $[\text{Ar}]\,3d^3 4s^2$: three single $3d$ electrons, so $3$ unpaired.

Step 3. Manganese. $[\text{Ar}]\,3d^5 4s^2$: five single $3d$ electrons, so $5$ unpaired.