Asample of a substance containing only magnesium and chlorine was tested in the lab and was found to be composed of 74.5% chlorine by mass. if the total mass of the sample was 190.2 grams, what was the mass of the magnesium? a) 24.3 g b) 48.5 g c) 70.9 g d) 142 g i know the answer is b, but i don't understand

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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particle   p is an electron and particle q is a neutron