Seismic waves hope this helps.
The action force is you sitting on the chair and the reaction force is the gravity on the chair that is caused by you sitting on the chair
Methane CH4
ethane C2H6
propane C3H8
Butane C4H10
pentane C5H12
The subscriot 2 means that in the formula there are two parts of K, and the subscript 1 (implicit) for S, indicates that there is one part of S.
This is, the formula gives the ratio of the elements K and S in the compound, which is:
2 atoms of K : 1 atom of S.
Answer: there are 2 atoms of K and 1 atom of S in a molecule of K2S.
