What is the half-life of 99tc if a 500 g sample decays to 62.5 g in 639000 years

Calculate the percent composition by mass of each element in al(oh)3. use at least three significant figures.

A5.00 g of a in . g of at aa 5.00 g of b in . g of .?at .

The biomedical technique in which a part of the brain is destroyed with electric current is known as a. electroconvulsive therapy b. prefrontal lobotomy c. bilateral cingulotomy d. tardive dyskinesia