<P> A period 6 element is one of the chemical elements in the sixth row (or period) of the periodic table of the elements, including the lanthanides . The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns . The sixth period contains 32 elements, tied for the most with period 7, beginning with caesium and ending with radon . Lead is currently the last stable element; all subsequent elements are radioactive . For bismuth, however, its only primordial isotope, Bi, has a half - life of more than 10 years, over a billion times longer than the current age of the universe . As a rule, period 6 elements fill their 6s shells first, then their 4f, 5d, and 6p shells, in that order; however, there are exceptions, such as gold . </P> <P> This period contains the lanthanides, also known as the rare earths . Many lanthanides are known for their magnetic properties, such as neodymium . Many period 6 transition metals are very valuable, such as gold, however many period 6 other metals are incredibly toxic, such as thallium . Period 6 contains the last stable element, lead . All subsequent elements in the periodic table are radioactive . After bismuth, which has a half - life or more than 10 years, polonium, astatine, and radon are some of the shortest - lived and rarest elements known; less than a gram of astatine is estimated to exist on earth at any given time . </P> <Dl> <Dd> <Table> <Tr> <Th_colspan="3"> Chemical element </Th> <Th> Chemical series </Th> <Th> Electron configuration </Th> </Tr> <Tr> <Td> 55 </Td> <Td> Cs </Td> <Td> Caesium </Td> <Td> Alkali metal </Td> <Td> (Xe) 6s </Td> </Tr> <Tr> <Td> 56 </Td> <Td> Ba </Td> <Td> Barium </Td> <Td> Alkaline earth metal </Td> <Td> (Xe) 6s </Td> </Tr> <Tr> <Td> 57 </Td> <Td> La </Td> <Td> Lanthanum </Td> <Td> Lanthanide </Td> <Td> (Xe) 5d 6s </Td> </Tr> <Tr> <Td> 58 </Td> <Td> Ce </Td> <Td> Cerium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 59 </Td> <Td> Pr </Td> <Td> Praseodymium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 60 </Td> <Td> Nd </Td> <Td> Neodymium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 61 </Td> <Td> Pm </Td> <Td> Promethium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 62 </Td> <Td> Sm </Td> <Td> Samarium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 63 </Td> <Td> Eu </Td> <Td> Europium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 64 </Td> <Td> Gd </Td> <Td> Gadolinium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 65 </Td> <Td> Tb </Td> <Td> Terbium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 66 </Td> <Td> Dy </Td> <Td> Dysprosium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 67 </Td> <Td> Ho </Td> <Td> Holmium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 68 </Td> <Td> Er </Td> <Td> Erbium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 69 </Td> <Td> Tm </Td> <Td> Thulium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 70 </Td> <Td> Yb </Td> <Td> Ytterbium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 71 </Td> <Td> Lu </Td> <Td> Lutetium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 72 </Td> <Td> Hf </Td> <Td> Hafnium </Td> <Td> Transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 73 </Td> <Td> Ta </Td> <Td> Tantalum </Td> <Td> Transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 74 </Td> <Td> </Td> <Td> Tungsten </Td> <Td> Transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 75 </Td> <Td> Re </Td> <Td> Rhenium </Td> <Td> Transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 76 </Td> <Td> Os </Td> <Td> Osmium </Td> <Td> Transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 77 </Td> <Td> Ir </Td> <Td> Iridium </Td> <Td> Transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 78 </Td> <Td> Pt </Td> <Td> Platinum </Td> <Td> Transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 79 </Td> <Td> Au </Td> <Td> Gold </Td> <Td> Transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 80 </Td> <Td> Hg </Td> <Td> Mercury </Td> <Td> Post-transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 81 </Td> <Td> Tl </Td> <Td> Thallium </Td> <Td> Post-transition metal </Td> <Td> (Xe) 4f 5d 6s 6p </Td> </Tr> <Tr> <Td> 82 </Td> <Td> Pb </Td> <Td> Lead </Td> <Td> Post-transition metal </Td> <Td> (Xe) 4f 5d 6s 6p </Td> </Tr> <Tr> <Td> 83 </Td> <Td> Bi </Td> <Td> Bismuth </Td> <Td> Post-transition metal </Td> <Td> (Xe) 4f 5d 6s 6p </Td> </Tr> <Tr> <Td> 84 </Td> <Td> Po </Td> <Td> Polonium </Td> <Td> Post-transition metal </Td> <Td> (Xe) 4f 5d 6s 6p </Td> </Tr> <Tr> <Td> 85 </Td> <Td> At </Td> <Td> Astatine </Td> <Td> Metalloid </Td> <Td> (Xe) 4f 5d 6s 6p </Td> </Tr> <Tr> <Td> 86 </Td> <Td> Rn </Td> <Td> Radon </Td> <Td> Noble gas </Td> <Td> (Xe) 4f 5d 6s 6p </Td> </Tr> </Table> </Dd> </Dl> <Dd> <Table> <Tr> <Th_colspan="3"> Chemical element </Th> <Th> Chemical series </Th> <Th> Electron configuration </Th> </Tr> <Tr> <Td> 55 </Td> <Td> Cs </Td> <Td> Caesium </Td> <Td> Alkali metal </Td> <Td> (Xe) 6s </Td> </Tr> <Tr> <Td> 56 </Td> <Td> Ba </Td> <Td> Barium </Td> <Td> Alkaline earth metal </Td> <Td> (Xe) 6s </Td> </Tr> <Tr> <Td> 57 </Td> <Td> La </Td> <Td> Lanthanum </Td> <Td> Lanthanide </Td> <Td> (Xe) 5d 6s </Td> </Tr> <Tr> <Td> 58 </Td> <Td> Ce </Td> <Td> Cerium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 59 </Td> <Td> Pr </Td> <Td> Praseodymium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 60 </Td> <Td> Nd </Td> <Td> Neodymium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 61 </Td> <Td> Pm </Td> <Td> Promethium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 62 </Td> <Td> Sm </Td> <Td> Samarium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 63 </Td> <Td> Eu </Td> <Td> Europium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 64 </Td> <Td> Gd </Td> <Td> Gadolinium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 65 </Td> <Td> Tb </Td> <Td> Terbium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 66 </Td> <Td> Dy </Td> <Td> Dysprosium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 67 </Td> <Td> Ho </Td> <Td> Holmium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 68 </Td> <Td> Er </Td> <Td> Erbium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 69 </Td> <Td> Tm </Td> <Td> Thulium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 70 </Td> <Td> Yb </Td> <Td> Ytterbium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 6s </Td> </Tr> <Tr> <Td> 71 </Td> <Td> Lu </Td> <Td> Lutetium </Td> <Td> Lanthanide </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 72 </Td> <Td> Hf </Td> <Td> Hafnium </Td> <Td> Transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 73 </Td> <Td> Ta </Td> <Td> Tantalum </Td> <Td> Transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 74 </Td> <Td> </Td> <Td> Tungsten </Td> <Td> Transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 75 </Td> <Td> Re </Td> <Td> Rhenium </Td> <Td> Transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 76 </Td> <Td> Os </Td> <Td> Osmium </Td> <Td> Transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 77 </Td> <Td> Ir </Td> <Td> Iridium </Td> <Td> Transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 78 </Td> <Td> Pt </Td> <Td> Platinum </Td> <Td> Transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 79 </Td> <Td> Au </Td> <Td> Gold </Td> <Td> Transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 80 </Td> <Td> Hg </Td> <Td> Mercury </Td> <Td> Post-transition metal </Td> <Td> (Xe) 4f 5d 6s </Td> </Tr> <Tr> <Td> 81 </Td> <Td> Tl </Td> <Td> Thallium </Td> <Td> Post-transition metal </Td> <Td> (Xe) 4f 5d 6s 6p </Td> </Tr> <Tr> <Td> 82 </Td> <Td> Pb </Td> <Td> Lead </Td> <Td> Post-transition metal </Td> <Td> (Xe) 4f 5d 6s 6p </Td> </Tr> <Tr> <Td> 83 </Td> <Td> Bi </Td> <Td> Bismuth </Td> <Td> Post-transition metal </Td> <Td> (Xe) 4f 5d 6s 6p </Td> </Tr> <Tr> <Td> 84 </Td> <Td> Po </Td> <Td> Polonium </Td> <Td> Post-transition metal </Td> <Td> (Xe) 4f 5d 6s 6p </Td> </Tr> <Tr> <Td> 85 </Td> <Td> At </Td> <Td> Astatine </Td> <Td> Metalloid </Td> <Td> (Xe) 4f 5d 6s 6p </Td> </Tr> <Tr> <Td> 86 </Td> <Td> Rn </Td> <Td> Radon </Td> <Td> Noble gas </Td> <Td> (Xe) 4f 5d 6s 6p </Td> </Tr> </Table> </Dd>

The second metal in period 6 that starts with an e
find me the text answering this question