The atoms may be compared to the letters of the alphabet, which can be put together into innumerable ways to form words. So the atoms are combined in equal variety to form what are called molecules.

The chemist, whose science is immediately concerned with the combinations of atoms, has rarely found it necessary to discuss their shapes, and gives them no particular forms in his diagrams. That does not mean that the shapes are unimportant, but rather that the older methods could not define them.

Let us think of Nature as a builder, making all that we see out of atoms of a limited number of kinds, just as the builder of a house constructs it out of so many different kinds of things: bricks, slates, planks, panes of glass, and so on.

William Henry Bragg Quotes