Why do igneous rocks yield the most accurate radiometric ages, ...

[Frost2351]

Why do igneous rocks yield the most accurate radiometric ages, and what is the calculated date the
  actual age of? What will be an ideal response?

Question 2

If you start with an element with 1,000,000 parent atoms, how many parents and how many daughters
  will there be after 6 half-lives? What will be an ideal response?

[meganlapinski]

Answer to Question 1

As magma cools and begins to crystallize, radioactive parent atoms are separated from previously
formed daughter atoms. Some radioactive parent atoms are incorporated into the crystal structure of
certain minerals, but the stable daughter atoms are a different size and cannot fit into the crystal
structure of the same mineral as the parent atoms. Therefore, these minerals will contain radioactive
parent atoms but no stable daughter atoms. The time being measured is the time of crystallization of
the mineral that contains the radioactive atoms, which is the time when the magma was cooling.

Answer to Question 2

0: P=1,000,000, D=0; 1: P=500,000, D=500,000; 2: P=250,000, D=750,000; 3: P=125,000,
D=875,000; 4: P=62,5000, D=937,500; 5: P=31,250; D=968,750; 6: P=15,625, D=984,315.