How does heating or cooling air affect the air’s volume?

As the air gets warm, molecules start to vibrate and they start to run into each other which makes the space around each of the molecules. Since each molecule takes up more space when it moves, the air gets bigger to let that happen and the air becomes denser or lighter!

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.