Question

what does an atom means and in hydrogen how many neutrons protons and electron present

Answer 1

Number of energy levels that aHydrogen atom have is only 1 . There are isotopes of Hydrogen that docontain neutrons. For example, deuterium has one neutron and tritium has 2 neutrons. Hydrogen have 1electrons,1 protons and 0 neutrons.

Answer 2

atom is the smallest constituent unit of matter.

in hydrogen:- 0 neutron + 1 proton + 1 electron is present.