determine the isotope produced in the beta decay of iodine-131 an isotope used to check thyroid gland function

Answer 1

212Rn86 ---> AXZ + 4He2

Answer 2

The way to solve these problems is simple. The left number is the mass number(jprotons + neutrons) and the right number is the atomic number (total protons). The left numbers must add up on both sides of the equation and the right numbers must do the same.
212Rn86 ---> AXZ + 4He2
You have 212 on the left for reactants. So A must be 212 -4 = 208
You have 86 on the right for reactants. So Z must be 86-2 = 84
So X must be the element with atomic number 84.Look on the periodic table and see that is Ac. AXZ would be written as 208Ac84.
I'll leave that first one for you. It's done the same way.

Answer 3

thank you.