Ever wondered what makes Hydrogen number 1 on the periodic table? There's a reason. Discover the intelligent design of the periodic table with BBC Bitesize. ... A zig-zag line divides them.

Spatially confined liquid crystals exhibit non-uniform alignment, often accompanied by self-organised topological defects of non-trivial shape in response to imposed boundary conditions and geometry.

A zig-zag line divides them. In most periodic tables hydrogen (H) is shown separately but is still classified as a non-metal. Hydrogen is placed on its own as it is quite a unique element.