Answer:
In molecular hydrogen, H2H2, the two hydrogen atoms are joined by a nonpolar covalent bond. There’s a lot to unpack in that term, so let’s get started.
What is a covalent bond? A covalent bond happens when two atoms share electrons. (Compare it to an ionic bond, which happens when one atom loses electrons to the other atom.) In a single covalent bond, each atom shares one electron with the other atom, so there are a pair of electrons that simultaneously belong to both atoms.
Sometimes the atoms share electrons evenly; sometimes they don’t. If one of the atoms has a greater attraction for electrons than the other atom does, the electrons are drawn more strongly to one side of the bond than to the other. We call that a polar covalent bond. But in the case of H2H2, where both atoms are exactly the same, the electrons are evenly distributed. That’s called a nonpolar covalent bond.
If you want to get even more technical, you could say that the bond between the hydrogen atoms is a sigma bond. Covalent bonds happen when atoms’ orbitals overlap. (Orbitals are the regions where electrons are most likely to be found.) A sigma bond is formed when the area of overlap is directly between the two atomic centers. (Orbitals can also overlap side-to-side, which is called a pi bond, but that’s not what happens in a hydrogen molecule.)
