Final answer:
The electron transport chain pumps hydrogen ions across the inner membrane to create a concentration gradient.
Step-by-step explanation:
The part of the electron transport chain that yields a H+ gradient across the inner membrane is the process of pumping hydrogen ions (H+) from the matrix into the intermembrane space of the mitochondria. This process occurs as high-energy electrons from NADH and FADH2 are transferred along the electron transport chain, releasing energy that is used to pump the hydrogen ions. The accumulation of these hydrogen ions in the intermembrane space creates a concentration gradient that is essential for ATP synthesis through chemiosmosis.