Arock formed with 1,000 atoms of a radioactive parent element, but only contains 12.5% of its original radioactive parent atoms today. if the half-life is 1,000,000 years, how old is the rock? (ess 4.6)

each  column  of the  table  is called a group. elements in a group share similar properties. groups are  read  from  top  to  bottom. metal. metalloid. nonmetal. solid. liquid. gas. fe. hg. o.  2. 3. 4. 5. 6. 7. 8. 9.  2. beryllium. 9.012. 4.  sodium. 22.990.  11. 3.  magnesium. 24.305.  12.  potassium. 39.098.  19. 4.  calcium. 40.078.  20. i guess  i  

the answer is d.) potassium