Video narration
How can one kind of atom make so many different substances? Carbon atoms are like snap-together building blocks. In compounds, each carbon usually makes four connections, called covalent bonds: links formed when atoms share electrons. Like a block with several joining points, carbon connects to other atoms and to other carbon atoms. Those carbon-to-carbon links can form chains or rings, with other atoms attached. Change which pieces connect, or their arrangement, and you get different compounds. The comparison is only about connections; atoms aren't blocks, and it doesn't show their real shape or scale. The variety doesn't come from carbon changing into different elements. It comes from the same pieces connecting in different ways. Because, like snap-together blocks, carbon forms four bonds-including bonds to other carbon atoms-so the same pieces can make many substances.