It is given that when a boron nucleus (510​ B) is bombarded by a neutron, an α-particle is emitted.Let X nucleus be formed as a result of the bombardment.According to the charge and mass conservation, Charge :  Mass : ​510​B+01​n→510​X+24​He01​3​7​​24​ The mass number of X should be 7 and its atomic number should be 3.∴X=37​Li