Question

black hole is made up of which atom

Answer 1

These guys say that dark matter is composed of black hole atoms—microscopic black holes with a charge that have somehow captured an electron or proton leaving them electrically neutral.

Answer 2

A black hole is a very odd thing; a remnant of an old star, it has mass but no atoms. The stuff of which it is made is so dense that it warps space and time; no ordinary matter can escape its enormous gravitational pull, not even light. Because you cannot see a black hole directly, scientists can only observe them through their effects on nearby stars.