In 1919 Rutherford hit nitrogen-14 with alpha particles and made oxygen-17 and a proton…

Step 1. The masses. Before: $14.003074\ \text{u} + 4.002603\ \text{u} = 18.005677$ u. After: $16.999132\ \text{u} + 1.007825\ \text{u} = 18.006957$ u.

Step 2. The Q value. The mass before minus the mass after is $-0.001280$ u. So $Q = -0.001280\ \text{u} \times 931.494\ \text{MeV/u} = -1.192$ MeV. The products are heavier, so the reaction is endothermic.

Step 3. The threshold. $K_\text{th} = 1.192\ \text{MeV} \times \dfrac{4.002603 + 14.003074}{14.003074} = 1.192\ \text{MeV} \times 1.2861 = 1.533$ MeV.