Leukocytes or white blood cells typically make up 4000-10,000 WBCs for every microliter of blood. If your white blood cell count drops below 3500 WBCs for every microliter of blood it causes a condition called leukopenia that causes cramps, fever, sore gums, diarrhea, sneezing, headaches, sore throat, etc.
Magnesium (Mg) naturally occurs in three stable isotopes, 24 Mg, 25 Mg, and 26 Mg. There are 19 radioisotopes that have been discovered, ranging from 19 Mg to 40 Mg. The longest-lived radioisotope is 28 Mg with a half-life of 20.915 hours. The lighter isotopes mostly decay to isotopes of sodium while the heavier isotopes decay to isotopes of aluminium. The shortest-lived is 39 Mg with a half-life shorter than 180 nanoseconds, or possibly 40 Mg, with a half-life longer than 170 nanoseconds (the half-life of 19 Mg is unknown). Standard atomic mass: 24.3050(6) u. A chart showing the abundances of the naturally-occurring isotopes of magnesium.
The half Life of a radioactive element is the time it takes for half of a sample of the element to break down. After about a million years, only 5 grams of a 10-gram sample of technetium-97 would remain. After another million years, only half of that, or 2.5 grams, would be left.