Google says 11 lol full google answer:
Sodium-23 atom is the stable isotope of sodium with relative atomic mass 22.989770, 100 atom percent natural abundance and nuclear spin 3/2. A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.
Answer:
I think temperature. sorry if the answer is wrong
The number of years required for 1/4 cobalt-60 to remain after decay is calculated as follows
after one half life 1/2 of the original mass isotope remains
after another half life 1/4 mass of original mass remains
therefore if one half life is 5.3 years then the years required
= 2 x 5.3years = 10.6 years
