That is true, you limit on what you can do with them.
(D)an atom can join with other kinds of atoms.
Basically he explained what a molecule is.
An hypothesis is a possible explanation for a set of observations or answer to a scientific question. A supposition or proposed explanation made on the
basis of limited evidence as a starting point for further
investigation.
And practically, an hypothesis is used as the basis for further experiments, where the hypothesis is rigorously tested under varying conditions. The hypothesis that is tested and modified under different conditions may become a general
theory
.The hypothesis that has the least number of variables sufficient to explain the phenomenon is preferred.