Write a word equation and a balanced symbol equation for the
combustion of hydrogen.

The balanced equation is: 2H2 (g) + O2 (g) -> 2H2O (g).

Explanation:

So to balance the equation, you have to make sure there are the same number of hydrogen and oxygen atoms on both sides of the equation.

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.