The half – life of a radioisotope is four hours. If the initial mass of the isotope was 200 g, the mass remaining after 24 hours undecayed is

Which one of the following ores is best concentrated by froth – floatation method?

Which among the following factors is the most important in making fluorine the strongest oxidizing halogen?

Beryllium and aluminium exhibit many properties which are similar. But the two elements differ in :