Every Element Is Unique:

Atoms of different elements are always dissimilar. The slightest change in an atom can make an incredible difference in its behavior. You can live by breathing pure oxygen though you cannot live off of pure nitrogen. Oxygen will cause metal to rust, but nitrogen will not. The wood will burn furiously in an environment of pure oxygen but will not even catch fire in pure nitrogen. Though, both look, feel, and smell exactly similar at normal temperature and pressure. Both are invisible gases, both are odorless, both are colorless, and both are just about equally heavy. Such substances are too different since oxygen and nitrogen consist of various numbers of or else identical particles.

There are many other illustrations in nature where a tiny change in atomic structure makes a main difference in the manner a substance behaves.