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.
A:Psychology degrees are offered at various levels of education. An associate degree in psychology is an undergraduate-level program that typically takes 2 years to complete. On the other hand, a bachelor's degree in psychology takes 4 years to complete. As for higher qualifications, you have the option of a master's in psychology that can take between 2 and 3 years.