By how much do the two members of a conjugate acid base pair differ?

1. Look at the forward and the reverse reaction of the same reversible equation. 2. An acid gives away a proton in the forward direction, leaving a species that can take one back. 3. That pair of species differs by exactly one hydrogen ion and by one unit of charge. 4. The species left after the acid loses its proton is the conjugate base of that acid. 5. Two hydrogen ions would take a diprotic acid two steps, which is not what a single pair describes. _Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Chapter 9: Acids and bases_