Group 18 is known as the Noble/ Inert Gases
You would want to make sure that you have controlled the variables properly, and if you determine that you did then you would repeat the experiment to be sure of the results.
A hydrated substance will decrease in mass when heated since the water is being boiled away.
I hope this helps. Let me know if anything is unclear.
Answer:
The two elements are POLONIUM and RADIUM.
Explanation:
Maria Curie is a French physicist and chemist, though she was of a Polish naturals. She was the first woman to receive a Noble Price which she earned for conducting leading and head way research on radioactivity. She discovered the theory of radioactivity; also the techniques isolating radioactive isotopes. These helped her and her husband discover Polium and Radium.