What is in phisical science, an atom's central reagon

What is a subatomic particle that has no change and that is found in the nuclaes of an atom

What is the sum of portrons and neutrons inthe neucleas of an atom

What is the mass of an atom expressed in atomic mass units

What is an atom that has the same number portrons (or the same atomic mass unit) as other atoms of the same element do butthat hasa different number of neutrons (and thus a different atomic mass uni