Which activity would be an appropriate first step when designing an experiment?

The appropriate initial step when you design an experiment is number (2). It is doing research about the problem utilizing information from different reliable sources. Among all the choices, this is the first step that should be done because you have to know everything about the problem first before the other 3 steps are done.

I think you are talking about the Scientific Method. The first step is to Ask A Question.

Here's what you do next:
2. Research.
3. Make a hypothesis.
4. Experiment while controlling variables.
5. Analyze data and make a conclusion.
6. Communicate your findings.

(If the experiment doesn't work, try, try again!)

Answer : option a) 84explanation :

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.

The answer for this is a