A quantum system can have separated allowed energies instead of a continuous ladder. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Allowed energies are separated
The diagram shows allowed energy levels, not every height between them. The labels are training levels, not real atom constants.
allowed levels are separated
A shifted level table shows the gaps
Taking the ground level as the zero reference, the same three allowed levels become a small exact table. The spacing is not uniform.
level012E04398
A level gap has an exact size
The middle to ground gap is 3/4 of the chosen energy unit.