Why does the chain of fusion reactions terminate when a star's core becomes pure Iron (Fe)?

Answer

Fusing iron consumes energy instead of releasing it.

Iron has the most tightly bound nucleus in the periodic table; fusing iron nuclei together requires an input of energy rather than releasing the energy necessary to counteract gravitational collapse.

Why does the chain of fusion reactions terminate when a star's core becomes pure Iron (Fe)?
Elementstarformationnucleosynthesisastrophysic