This is carbon number two. This is carbon number three, carbon number 3456 and so forth. Now, notice that we actually have a mixture of two types of isomers, and we form this mixture of two types of isomers we call atomers, the alpha atomer and the beta atomer. Because this nucleophile can attack the carbon either from the top side or from the bottom side. When it attacks from the top side, it forms one of these. When it talks from the bottom side, it forms the other isomer.