Suppose the half-life of an isotope is 10 years. after how many years will half of this isotope have decayed into its daughter elements?

5 years
10 years
20 years

Becquerel expected to find ( he developed the photographic plate that had sun-exposed minerals on top of it. becquerel expected to find ( he developed the photographic plate that had been in the closed drawer.

What are the first two quantum numbers for the electrons located in subshell 4d? what are the first three quantum numbers for the electrons located in subshell 2s? how many electrons can be held in a sublevel l = 3? how many electrons can be held in the energy level n = 4? how many electrons in an atom can share the quantum numbers n = 4 and l = 3?

Word equation for k(s)+h2o(l) yield koh(aq) + h2(g)