The rare-earth elements , also called the rare-earth metals or in context rare-earth oxides , or the lanthanides though yttrium and scandium are usually included as rare-earths are a set of 17 nearly indistinguishable lustrous silvery-white soft heavy metals. The ending "-ide" normally indicates a negative ion. However, owing to wide current usage, "lanthanide" is still allowed and is roughly analogous to rare earth element. In pure form, these metals tarnish slowly in air at room temperature, and react slowly with cold water to form hydroxides, liberating hydrogen.
18.5D: Carbon Dating and Estimating Fossil Age
How Carbon Dating Works | HowStuffWorks
Despite the name, it does not give an absolute date of organic material - but an approximate age, usually within a range of a few years either way. There are three carbon isotopes that occur as part of the Earth's natural processes; these are carbon, carbon and carbon The unstable nature of carbon 14 with a precise half-life that makes it easy to measure means it is ideal as an absolute dating method. The other two isotopes in comparison are more common than carbon in the atmosphere but increase with the burning of fossil fuels making them less reliable for study 2 ; carbon also increases, but its relative rarity means its increase is negligible. The half-life of the 14 C isotope is 5, years, adjusted from 5, years originally calculated in the s; the upper limit of dating is in the region of , years, after which the amount of 14 C is negligible 3.
Why is carbon-14 dating not used for dating dinosaur bones/fossils?
This is how carbon dating works: Carbon is a naturally abundant element found in the atmosphere, in the earth, in the oceans, and in every living creature. C is by far the most common isotope, while only about one in a trillion carbon atoms is C C is produced in the upper atmosphere when nitrogen N is altered through the effects of cosmic radiation bombardment a proton is displaced by a neutron effectively changing the nitrogen atom into a carbon isotope. The new isotope is called "radiocarbon" because it is radioactive, though it is not dangerous. It is naturally unstable and so it will spontaneously decay back into N after a period of time.
A fossil from Classical Latin : fossilis , literally "obtained by digging"  is any preserved remains, impression, or trace of any once- living thing from a past geological age. Examples include bones , shells , exoskeletons , stone imprints of animals or microbes , objects preserved in amber , hair , petrified wood , oil , coal , and DNA remnants. The totality of fossils is known as the fossil record. Paleontology is the study of fossils: their age, method of formation, and evolutionary significance.