Pulling on a shared pair

A shared pair sits between two atoms, but it does not have to sit halfway between them. Which atom it leans towards depends on electronegativity.

This is the same property that decided the ionic chapter. Sodium had a low value and gave its electron away; chlorine had a high one and took it. Here the difference is smaller, so no transfer happens — but the pull is still there.

When both atoms pull equally

A hydrogen molecule is two hydrogen atoms joined by a covalent bond. Both are the same element, so both have exactly the same electronegativity, and each pulls on the shared pair precisely as hard as the other.

Neither side wins, so the bonding electrons are spread symmetrically. There is no end of the molecule where negative charge has gathered and no end where it is short.