TABLE 9 sotopes Frequently used in Radiometric Dating Radioactive Parent Uranium 238 Uranium 235 Thorium 232 Rubidium 87 Potassium 40 1 3 billion years 500 million years 3 9 billion years 2 6 billion years Stable Daughter Product Lead 206 Lead 207 Lead 208 Strontium 87 Argon 40 Currently Accepted Half Life Values 4 5 billion years 704 million years 14 1 billion years 47 0 billion years 1 3 billion years