<P> Of the seventeen rare - earth elements (REEs), fifteen belong to the lanthanide series . The other two, scandium and yttrium, are listed in the table above, as are three lanthanides: lanthanum, cerium, and samarium . Of the remaining twelve lanthanides, eleven are listed below . No information is available regarding the remaining lanthanide, the highly radioactive promethium . </P> <P> Concentration of rare - earth elements / lanthanides in blood serum . </P> <Table> <Tr> <Th> Atomic number </Th> <Th> Element </Th> <Th> g / ml blood serum </Th> <Th> Atomic percent </Th> <Th> Positive health role in mammals </Th> <Th> Negative effects of excess </Th> <Th> Group </Th> </Tr> <Tr> <Td> 59 </Td> <Td> Praseodymium </Td> <Td> 6989110000000000000 ♠ 11 × 10 </Td> <Td> </Td> <Td> </Td> <Td> low to moderate toxicity </Td> <Td> n / a </Td> </Tr> <Tr> <Td> 60 </Td> <Td> Neodymium </Td> <Td> 6989337000000000000 ♠ 33.7 × 10 </Td> <Td> </Td> <Td> </Td> <Td> low to moderate toxicity </Td> <Td> n / a </Td> </Tr> <Tr> <Td> 63 </Td> <Td> Europium </Td> <Td> 6989820000000000000 ♠ 82 × 10 </Td> <Td> </Td> <Td> </Td> <Td> comparable to other heavy metals </Td> <Td> n / a </Td> </Tr> <Tr> <Td> 64 </Td> <Td> Gadolinium </Td> <Td> 6988720000000000000 ♠ 7.2 × 10 </Td> <Td> </Td> <Td> </Td> <Td> free ions highly toxic </Td> <Td> n / a </Td> </Tr> <Tr> <Td> 65 </Td> <Td> Terbium </Td> <Td> 6988130000000000000 ♠ 1.3 × 10 </Td> <Td> </Td> <Td> </Td> <Td> low to moderate toxicity </Td> <Td> n / a </Td> </Tr> <Tr> <Td> 66 </Td> <Td> Dysprosium </Td> <Td> 6988960000000000000 ♠ 9.6 × 10 </Td> <Td> </Td> <Td> </Td> <Td> mildly toxic when ingested </Td> <Td> n / a </Td> </Tr> <Tr> <Td> 67 </Td> <Td> Holmium </Td> <Td> 6988255000000000000 ♠ 2.55 × 10 </Td> <Td> </Td> <Td> </Td> <Td> low acute toxicity </Td> <Td> n / a </Td> </Tr> <Tr> <Td> 68 </Td> <Td> Erbium </Td> <Td> 6988950000000000000 ♠ 9.5 × 10 </Td> <Td> </Td> <Td> </Td> <Td> low to moderate toxicity </Td> <Td> n / a </Td> </Tr> <Tr> <Td> 69 </Td> <Td> Thulium </Td> <Td> 6988169000000000000 ♠ 1.69 × 10 </Td> <Td> </Td> <Td> </Td> <Td> soluble salts slightly toxic in large amounts </Td> <Td> n / a </Td> </Tr> <Tr> <Td> 70 </Td> <Td> Ytterbium </Td> <Td> 6989132000000000000 ♠ 13.2 × 10 </Td> <Td> </Td> <Td> </Td> <Td> all compounds highly toxic </Td> <Td> n / a </Td> </Tr> <Tr> <Td> 71 </Td> <Td> Lutetium </Td> <Td> 6988246000000000000 ♠ 2.46 × 10 </Td> <Td> </Td> <Td> </Td> <Td> oxide powder is toxic </Td> <Td> n / a </Td> </Tr> </Table> <Tr> <Th> Atomic number </Th> <Th> Element </Th> <Th> g / ml blood serum </Th> <Th> Atomic percent </Th> <Th> Positive health role in mammals </Th> <Th> Negative effects of excess </Th> <Th> Group </Th> </Tr>

Where is the most gold found in the human body