Yes, the dark mass is the chick
You don't always get much movement at this stage. An infertile egg is called a 'clear' egg for just that reason - it's clear, you can see nothing really inside.
If you candle again just before they're due you'll see a much bigger air sac and the rest of the egg completely dark as the chick has filled it. Sometimes you can see the beak chipping away inside
Occasionally an egg will stop developing part way along. Then you can see too much 'unused up egg contents' and less chick, compared with the others.