Which is a way that paleontologists have contributed to humans' understanding of the history of life? They found evidence that climate has not changed significantly. They grouped organisms by the period in which they existed. They discovered that the first humans lived with dinosaurs. They learned that life has existed since Earth was created.

answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.

what is the question here. i think you messed up.

answersilicon (si); oxygen (o);

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.