What critical element forms in the core of a massive star just before its final gravitational collapse triggers a supernova?

Answer

Iron

The multi-shell fusion chain reaction in massive stars culminates when the core becomes composed primarily of iron; fusing iron requires energy input rather than releasing it, causing the sudden loss of outward pressure.

What critical element forms in the core of a massive star just before its final gravitational collapse triggers a supernova?
evolutionprocessstarFusion