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.
Some students may also earn a master's degree in psychology, but many doctorate programs do not require it. After youâve been admitted to a graduate program, it generally takes at least four years to earn a Ph.D. and another year to complete an internship. Once these requirements have been fulfilled, students can take state and national exams to become licensed to practice psychology in the state where they wish to work.