Your teacher asks you to follow the instructions in a lab to produce several known chemical reactions. During these procedures,
you are required to record any observations that suggest chemical reactions have occurred. Which of these list of observations best
describes evidence of chemical reactions?
a. a liquid melts and becomes a solid.
b. when heated steam comes out of a test tube.
c. a gas or solid is formed from two liquid solutions.
d. the two chemicals separate and form two distinct layers.

how to make a simple air condition

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.

answerambulatory;