16. It is neutral. 17. It is positively-charged. 18.It is negatively-charged. 19. It revolves around the nucleus. 20. It is found in the nucleus of an atom. 21. It is responsible for the mass of an atom. 24. IC IS Discovered by I. i nomson. 23. It is discovered by Ernest Rutherford. 24. It is discovered by James Chadwick. 25. The lightest subatomic particles.