The energy released if hydrogen atoms are combined to form $$^{4}_{2}$$He is __________ MeV. (Take binding energies per nucleon of $$^{2}_{1}$$H and $$^{4}_{2}$$He as 1.1 MeV and 7.2 MeV, respectively)

$$Q = \text{Total B.E. of Products} - \text{Total B.E. of Reactants}$$

$$2 \left(_{1}^{2}\text{H}\right) \longrightarrow _{2}^{4}\text{He}$$

$$\text{B.E. of one } _{1}^{2}\text{H} = 2 \times 1.1\text{ MeV} = 2.2\text{ MeV}$$

$$\text{Total B.E. of Reactants} = 2 \times 2.2\text{ MeV} = 4.4\text{ MeV}$$

$$\text{Total B.E. of Products} = 4 \times 7.2\text{ MeV} = 28.8\text{ MeV}$$

$$Q = 28.8\text{ MeV} - 4.4\text{ MeV} = 24.4\text{ MeV}$$