It's composed of two carbons and a total of six H atoms. A methane molecule, however, is the simplest alkane. It's composed of one carbon and four H atoms, identical H atoms attached to the carbon via SP three hybridized orbitals. So we're basically going to take two methane molecules, combine them, and form our ethylene. But before we actually combine them, we have to turn them into methyl radicals. A methyl radical is simply a methane molecule minus an h atom and an electron.