Which of the following processes is endothermic? Any combustion reaction
Bonds being made in the products
Bonds being broken in the reactants

it is to be noted that an alpha particle is an helium nucleus. so it contains 2 protons 2 neutrons and has a mass number of 4. when alpha decay particles are ejected from the nucleus it gets transformed into an atom which has atomic number less than 2 and a mass number less than 4.

an equation that could represent alpha decay is radium 226 decay of alpha particle forms radon 222.

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that's what i got you can count the number of atoms