Are most nuclei stable? Chemistry Matter Basic Atomic Structure 1 Answer anor277 Dec 20, 2017 Well, yes.... Explanation: To a first approximation most matter in the universe is hydrogen, 75% by mass, and helium, 25% by mass.... And most isotopes of these elements are stable... Answer link Related questions How big is an electron compared with a proton? How many electrons would it take to equal the mass of a helium nucleus? How can I draw Bohr diagrams? How do protons determine the properties of an atom? How many neutrons can an atom have? What is the atomic structure of carbon? Why is the number of protons and electrons equal in an atom? Question #2b573 Question #a2716 Question #c0a6c See all questions in Basic Atomic Structure Impact of this question 1673 views around the world You can reuse this answer Creative Commons License