system
Given the following post, respond as if you're commenting on Reddit:
human
How/why do snowflakes form geometrically?
gpt
The shape and polarity of a water molecule has a lot to do with it.

The chemical formula is H2O, but it's structure is H-O-H. The thing is that it's not a straight chain. The angle is closer to 120, not 180 (extra electrons around the O take space and push the Hs together). 

From there, the 120 degree H-O-H works like a building block. Water is highly polar, with oxygen's electrons forming one pole and the positive Hs forming the other. The molecules link-up in the same way magnets would. The shapes of snowflakes are the shapes possible from the atomic "building blocks".

Even though polar attraction is linking the molecules, repulsive forces are also present. This creates fields across the chain, which will eventually "kink" and create the lattice structure of snowflakes. Again, those shapes are all permutations of the 120-degree H-O-H, forced into some regularity by polar forces.