Assertion: lead pencil's lead | /r/HasProperty | five stable isotopes
Facets:
value: with mass numbers
type: OTHER
Source sentences:
text: Natural lead is composed of five stable isotopes, with mass numbers 202 (trace), 204 (1.5 percent), 206 (23.6 percent), 207 (22.6 percent), and 208 (52.3 percent).