The carbon atom and hydrogen atoms are close together. The electrons from each atom feels the attraction from the proton in the nucleus of the other atom. This attraction pulls the atoms together and ...

But what makes oxygen different from carbon? It is the number of protons in the nucleus of an atom that is the defining feature of the atom. It's what makes one element different from another.

The picture shows a close-up of one carbon atom. A hydrogen atom has one proton as the nucleus and one electron in the region outside the nucleus. The electron and proton are attracted to each other.