Orbital

an electron is not a dot on a ring. turn one and see.

turn wax models of the real orbitals -- s, p, the three p, d and d z2 -- until each shows its shape and its nodes, then slide two atoms together on a rail until their lobes fuse into a sigma bond and a pi bond

Each model is the surface that holds 90% of where the electron can be found (the three p together are drawn at 30%, so they do not hide each other): s is a sphere, p two lobes of opposite sign (the colours) with a flat node between, d four lobes with two nodes, and d z² a dumbbell through a doughnut whose nodes are cones. Two atoms bond where their lobes overlap with the same sign; opposite signs cancel and push apart. End-on is a sigma bond; side-on is a pi, with a flat node through both atoms.

Concepts: quantum-mechanics, atomic-structure.

An interactive you play with one thumb, on Wundr.