Answer:
1) Constructive Interference
2) Hits a surface and bounces back
3) Antinodes
Answer:
I think #3 might be the answer .
Because in #1 atomic mass tells mass .
#4 Atomic number doesnot only tell about the electrons atom has
Uncertainty of the data hope its help you
C. Ne
down here is the list of monoatomic elements, just for you :)