Unlike chemical reactions, for which mass is conserved, nuclear reactions result in slight changes in mass. When mass is lost, it becomes energy according to the equation where is the energy in joules, is the mass defect in kilograms, and is the speed of light (). The mass defect is the difference between the total mass of the products and the total mass of reactants. The following values can be used to calculate the mass defect. Particle Mass () 0.00054858 1.00782 4.00260