Thus by 1803 there were two known rare earth elements, yttrium and cerium, although it took another 30 years for researchers to determine that other elements were contained in the two ores ceria and yttria (the similarity of the rare earth metals' chemical properties made their separation difficult).
For instance, students who pursue a Ph.D. in psychology usually take from five to seven years depending upon required coursework as well as internship and supervised residency requirements.
Master's Degree in Psychology. A master's degree in psychology is a graduate-level degree that often takes between two and three years beyond the bachelor's degree to complete. Like the bachelor's degree, students can usually choose between a Master of Arts (M.A.) or Master of Science (M.S.) in psychology. Jobs at the master's level are far more plentiful than those at the bachelor's level, which is why this is one of the most popular degree options.