Evidence of chemical reactions include - light production, color change (new/different), gas production (bubbles/fizzing - not boiling), precipitate, and temperature change

no light production, color change (new/different), gas production (bubbles/fizzing - not boiling), precipitate, and temperature stays the same

color change (new/different), gas production (like when a soda is opened), precipitate, and temperature stays the same

light production, color change (like adding food coloring to water), gas production (like when a soda is opened), precipitate, and temperature change

metric time was an attempt to create a standard unit of time based off of 10, but it never took off an is not included in the metric system (si)

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.