n. Symbol Cm A silvery metallic synthetic radioactive transuranic element, having isotopes with mass numbers ranging from 233 to 252. The most stable isotope (Cm-247) has a half-life of 15.6 million years. Atomic number 96; melting point 1,345°C; specific gravity (calculated) 13.51; valence 3, 4. See Periodic Table. [After Marie Curie and Pierre Curie.] |
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.