Known Aliases: Ra Element 88 Distinguishing Features: Density: 5 grams per cubic centimeterMelting point: 1292 dg. Fahrenheit Boiling Point: 2084 dg. Fahrenheit Common Ions & Isotopes: Radium has 33 isotopes whose half-lives are known they have mass numbers ranging from 202-234 none are stable. 226 Ra has the longest half-life of 1602 years.