Compare rhyolite to basalt (answer in one word only): Which has a lower density? Which has a lighter color? Which has a more mafic composition? Which has a greater percentage of biotite in it? Which contains Quartz?

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.