Assertion: atom's nucleus | /r/HasProperty | proton
Facets:
Source sentences:
text: It was known that the nucleus was composed of protons and neutrons and that protons possessed positive electric charge, while neutrons were electrically neutral.
text: Alpha particles represent the nuclei of helium atoms, comprised of two protons and two neutrons.
text: The nucleus is made of one or more protons and a number of neutrons.