Assertion: astatine's isotope | /r/HasAspect | 20 protons
Facets:
Source sentences:
text: The JINR team sought to use berkelium because calcium-48, the isotope of calcium used in the beam, has 20 protons and 28 neutrons, making a neutron–proton ratio of 1.4; and it is the lightest stable or near-stable nucleus with such a large neutron excess.