{"Element":"hydrogen","Symbol":"H","Atomic number":"1","stdAW::Value":"[1.00784,1.00811]","abrStdAW::Value":1.008,"abrStdAW::±":0.0002,"Note":"Modified isotopic compositions may be found in commercially available material because the material has been subjected to some undisclosed or inadvertent isotopic fractionation. Substantial deviations in atomic weight of the element from that given in the table can occur."}
{"Element":"helium","Symbol":"He","Atomic number":"2","stdAW::Value":"4.002602","stdAW::Uncertainty":2e-06,"abrStdAW::Value":4.0026,"abrStdAW::±":0.0001,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty.\nRange in isotopic composition of normal terrestrial material prevents a more precise standard atomic weight being given; the tabulated value and uncertainty should be applicable to normal material."}
{"Element":"lithium","Symbol":"Li","Atomic number":"3","stdAW::Value":"[6.938,6.997]","abrStdAW::Value":6.94,"abrStdAW::±":0.06,"Note":"Modified isotopic compositions may be found in commercially available material because the material has been subjected to some undisclosed or inadvertent isotopic fractionation. Substantial deviations in atomic weight of the element from that given in the table can occur."}
{"Element":"beryllium","Symbol":"Be","Atomic number":"4","stdAW::Value":"9.0121831","stdAW::Uncertainty":5e-07,"abrStdAW::Value":9.0122,"abrStdAW::±":0.0001}
{"Element":"boron","Symbol":"B","Atomic number":"5","stdAW::Value":"[10.806,10.821]","abrStdAW::Value":10.81,"abrStdAW::±":0.02,"Note":"Modified isotopic compositions may be found in commercially available material because the material has been subjected to some undisclosed or inadvertent isotopic fractionation. Substantial deviations in atomic weight of the element from that given in the table can occur."}
{"Element":"carbon","Symbol":"C","Atomic number":"6","stdAW::Value":"[12.0096,12.0116]","abrStdAW::Value":12.011,"abrStdAW::±":0.002}
{"Element":"nitrogen","Symbol":"N","Atomic number":"7","stdAW::Value":"[14.00643,14.00728]","abrStdAW::Value":14.007,"abrStdAW::±":0.001,"Note":"Modified isotopic compositions may be found in commercially available material because the material has been subjected to some undisclosed or inadvertent isotopic fractionation. Substantial deviations in atomic weight of the element from that given in the table can occur."}
{"Element":"oxygen","Symbol":"O","Atomic number":"8","stdAW::Value":"[15.99903,15.99977]","abrStdAW::Value":15.999,"abrStdAW::±":0.001,"Note":"Modified isotopic compositions may be found in commercially available material because the material has been subjected to some undisclosed or inadvertent isotopic fractionation. Substantial deviations in atomic weight of the element from that given in the table can occur."}
{"Element":"fluorine","Symbol":"F","Atomic number":"9","stdAW::Value":"18.998403162","stdAW::Uncertainty":5e-09,"abrStdAW::Value":18.998,"abrStdAW::±":0.001}
{"Element":"neon","Symbol":"Ne","Atomic number":"10","stdAW::Value":"20.1797","stdAW::Uncertainty":0.0006,"abrStdAW::Value":20.18,"abrStdAW::±":0.001,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty.\nModified isotopic compositions may be found in commercially available material because the material has been subjected to some undisclosed or inadvertent isotopic fractionation. Substantial deviations in atomic weight of the element from that given in the table can occur."}
{"Element":"sodium","Symbol":"Na","Atomic number":"11","stdAW::Value":"22.98976928","stdAW::Uncertainty":2e-08,"abrStdAW::Value":22.99,"abrStdAW::±":0.001}
{"Element":"magnesium","Symbol":"Mg","Atomic number":"12","stdAW::Value":"[24.304,24.307]","abrStdAW::Value":24.305,"abrStdAW::±":0.002}
{"Element":"aluminium","Symbol":"Al","Atomic number":"13","stdAW::Value":"26.9815384","stdAW::Uncertainty":3e-07,"abrStdAW::Value":26.982,"abrStdAW::±":0.001}
{"Element":"silicon","Symbol":"Si","Atomic number":"14","stdAW::Value":"[28.084,28.086]","abrStdAW::Value":28.085,"abrStdAW::±":0.001}
{"Element":"phosphorus","Symbol":"P","Atomic number":"15","stdAW::Value":"30.973761998","stdAW::Uncertainty":5e-09,"abrStdAW::Value":30.974,"abrStdAW::±":0.001}
{"Element":"sulfur","Symbol":"S","Atomic number":"16","stdAW::Value":"[32.059,32.076]","abrStdAW::Value":32.06,"abrStdAW::±":0.02}
{"Element":"chlorine","Symbol":"Cl","Atomic number":"17","stdAW::Value":"[35.446,35.457]","abrStdAW::Value":35.45,"abrStdAW::±":0.01,"Note":"Modified isotopic compositions may be found in commercially available material because the material has been subjected to some undisclosed or inadvertent isotopic fractionation. Substantial deviations in atomic weight of the element from that given in the table can occur."}
{"Element":"argon","Symbol":"Ar","Atomic number":"18","stdAW::Value":"[39.792,39.963]","abrStdAW::Value":39.95,"abrStdAW::±":0.16}
{"Element":"potassium","Symbol":"K","Atomic number":"19","stdAW::Value":"39.0983","stdAW::Uncertainty":0.0001,"abrStdAW::Value":39.098,"abrStdAW::±":0.001}
{"Element":"calcium","Symbol":"Ca","Atomic number":"20","stdAW::Value":"40.078","stdAW::Uncertainty":0.004,"abrStdAW::Value":40.078,"abrStdAW::±":0.004,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"scandium","Symbol":"Sc","Atomic number":"21","stdAW::Value":"44.955907","stdAW::Uncertainty":4e-06,"abrStdAW::Value":44.956,"abrStdAW::±":0.001}
{"Element":"titanium","Symbol":"Ti","Atomic number":"22","stdAW::Value":"47.867","stdAW::Uncertainty":0.001,"abrStdAW::Value":47.867,"abrStdAW::±":0.001}
{"Element":"vanadium","Symbol":"V","Atomic number":"23","stdAW::Value":"50.9415","stdAW::Uncertainty":0.0001,"abrStdAW::Value":50.942,"abrStdAW::±":0.001}
{"Element":"chromium","Symbol":"Cr","Atomic number":"24","stdAW::Value":"51.9961","stdAW::Uncertainty":0.0006,"abrStdAW::Value":51.996,"abrStdAW::±":0.001}
{"Element":"manganese","Symbol":"Mn","Atomic number":"25","stdAW::Value":"54.938043","stdAW::Uncertainty":2e-06,"abrStdAW::Value":54.938,"abrStdAW::±":0.001}
{"Element":"iron","Symbol":"Fe","Atomic number":"26","stdAW::Value":"55.845","stdAW::Uncertainty":0.002,"abrStdAW::Value":55.845,"abrStdAW::±":0.002}
{"Element":"cobalt","Symbol":"Co","Atomic number":"27","stdAW::Value":"58.933194","stdAW::Uncertainty":3e-06,"abrStdAW::Value":58.933,"abrStdAW::±":0.001}
{"Element":"nickel","Symbol":"Ni","Atomic number":"28","stdAW::Value":"58.6934","stdAW::Uncertainty":0.0004,"abrStdAW::Value":58.693,"abrStdAW::±":0.001,"Note":"Range in isotopic composition of normal terrestrial material prevents a more precise standard atomic weight being given; the tabulated value and uncertainty should be applicable to normal material."}
{"Element":"copper","Symbol":"Cu","Atomic number":"29","stdAW::Value":"63.546","stdAW::Uncertainty":0.003,"abrStdAW::Value":63.546,"abrStdAW::±":0.003,"Note":"Range in isotopic composition of normal terrestrial material prevents a more precise standard atomic weight being given; the tabulated value and uncertainty should be applicable to normal material."}
{"Element":"zinc","Symbol":"Zn","Atomic number":"30","stdAW::Value":"65.38","stdAW::Uncertainty":0.02,"abrStdAW::Value":65.38,"abrStdAW::±":0.02,"Note":"Range in isotopic composition of normal terrestrial material prevents a more precise standard atomic weight being given; the tabulated value and uncertainty should be applicable to normal material."}
{"Element":"gallium","Symbol":"Ga","Atomic number":"31","stdAW::Value":"69.723","stdAW::Uncertainty":0.001,"abrStdAW::Value":69.723,"abrStdAW::±":0.001}
{"Element":"germanium","Symbol":"Ge","Atomic number":"32","stdAW::Value":"72.63","stdAW::Uncertainty":0.008,"abrStdAW::Value":72.63,"abrStdAW::±":0.008}
{"Element":"arsenic","Symbol":"As","Atomic number":"33","stdAW::Value":"74.921595","stdAW::Uncertainty":6e-06,"abrStdAW::Value":74.922,"abrStdAW::±":0.001}
{"Element":"selenium","Symbol":"Se","Atomic number":"34","stdAW::Value":"78.971","stdAW::Uncertainty":0.008,"abrStdAW::Value":78.971,"abrStdAW::±":0.008,"Note":"Range in isotopic composition of normal terrestrial material prevents a more precise standard atomic weight being given; the tabulated value and uncertainty should be applicable to normal material."}
{"Element":"bromine","Symbol":"Br","Atomic number":"35","stdAW::Value":"[79.901,79.907]","abrStdAW::Value":79.904,"abrStdAW::±":0.003}
{"Element":"krypton","Symbol":"Kr","Atomic number":"36","stdAW::Value":"83.798","stdAW::Uncertainty":0.002,"abrStdAW::Value":83.798,"abrStdAW::±":0.002,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty.\nModified isotopic compositions may be found in commercially available material because the material has been subjected to some undisclosed or inadvertent isotopic fractionation. Substantial deviations in atomic weight of the element from that given in the table can occur."}
{"Element":"rubidium","Symbol":"Rb","Atomic number":"37","stdAW::Value":"85.4678","stdAW::Uncertainty":0.0003,"abrStdAW::Value":85.468,"abrStdAW::±":0.001,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"strontium","Symbol":"Sr","Atomic number":"38","stdAW::Value":"87.62","stdAW::Uncertainty":0.01,"abrStdAW::Value":87.62,"abrStdAW::±":0.01,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty.\nRange in isotopic composition of normal terrestrial material prevents a more precise standard atomic weight being given; the tabulated value and uncertainty should be applicable to normal material."}
{"Element":"yttrium","Symbol":"Y","Atomic number":"39","stdAW::Value":"88.905838","stdAW::Uncertainty":2e-06,"abrStdAW::Value":88.906,"abrStdAW::±":0.001}
{"Element":"zirconium","Symbol":"Zr","Atomic number":"40","stdAW::Value":"91.224","stdAW::Uncertainty":0.002,"abrStdAW::Value":91.224,"abrStdAW::±":0.002,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"niobium","Symbol":"Nb","Atomic number":"41","stdAW::Value":"92.90637","stdAW::Uncertainty":1e-05,"abrStdAW::Value":92.906,"abrStdAW::±":0.001}
{"Element":"molybdenum","Symbol":"Mo","Atomic number":"42","stdAW::Value":"95.95","stdAW::Uncertainty":0.01,"abrStdAW::Value":95.95,"abrStdAW::±":0.01,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"technetium","Symbol":"Tc","Atomic number":"43","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"ruthenium","Symbol":"Ru","Atomic number":"44","stdAW::Value":"101.07","stdAW::Uncertainty":0.02,"abrStdAW::Value":101.07,"abrStdAW::±":0.02,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"rhodium","Symbol":"Rh","Atomic number":"45","stdAW::Value":"102.90549","stdAW::Uncertainty":0.00002,"abrStdAW::Value":102.91,"abrStdAW::±":0.01}
{"Element":"palladium","Symbol":"Pd","Atomic number":"46","stdAW::Value":"106.42","stdAW::Uncertainty":0.01,"abrStdAW::Value":106.42,"abrStdAW::±":0.01,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"silver","Symbol":"Ag","Atomic number":"47","stdAW::Value":"107.8682","stdAW::Uncertainty":0.0002,"abrStdAW::Value":107.87,"abrStdAW::±":0.01,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"cadmium","Symbol":"Cd","Atomic number":"48","stdAW::Value":"112.414","stdAW::Uncertainty":0.004,"abrStdAW::Value":112.41,"abrStdAW::±":0.01,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"indium","Symbol":"In","Atomic number":"49","stdAW::Value":"114.818","stdAW::Uncertainty":0.001,"abrStdAW::Value":114.82,"abrStdAW::±":0.01}
{"Element":"tin","Symbol":"Sn","Atomic number":"50","stdAW::Value":"118.71","stdAW::Uncertainty":0.007,"abrStdAW::Value":118.71,"abrStdAW::±":0.01,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"antimony","Symbol":"Sb","Atomic number":"51","stdAW::Value":"121.76","stdAW::Uncertainty":0.001,"abrStdAW::Value":121.76,"abrStdAW::±":0.01,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"tellurium","Symbol":"Te","Atomic number":"52","stdAW::Value":"127.6","stdAW::Uncertainty":0.03,"abrStdAW::Value":127.6,"abrStdAW::±":0.03,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"iodine","Symbol":"I","Atomic number":"53","stdAW::Value":"126.90447","stdAW::Uncertainty":0.00003,"abrStdAW::Value":126.9,"abrStdAW::±":0.01}
{"Element":"xenon","Symbol":"Xe","Atomic number":"54","stdAW::Value":"131.293","stdAW::Uncertainty":0.006,"abrStdAW::Value":131.29,"abrStdAW::±":0.01,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty.\nModified isotopic compositions may be found in commercially available material because the material has been subjected to some undisclosed or inadvertent isotopic fractionation. Substantial deviations in atomic weight of the element from that given in the table can occur."}
{"Element":"caesium","Symbol":"Cs","Atomic number":"55","stdAW::Value":"132.90545196","stdAW::Uncertainty":6e-08,"abrStdAW::Value":132.91,"abrStdAW::±":0.01}
{"Element":"barium","Symbol":"Ba","Atomic number":"56","stdAW::Value":"137.327","stdAW::Uncertainty":0.007,"abrStdAW::Value":137.33,"abrStdAW::±":0.01}
{"Element":"lanthanum","Symbol":"La","Atomic number":"57","stdAW::Value":"138.90547","stdAW::Uncertainty":0.00007,"abrStdAW::Value":138.91,"abrStdAW::±":0.01,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"cerium","Symbol":"Ce","Atomic number":"58","stdAW::Value":"140.116","stdAW::Uncertainty":0.001,"abrStdAW::Value":140.12,"abrStdAW::±":0.01,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"praseodymium","Symbol":"Pr","Atomic number":"59","stdAW::Value":"140.90766","stdAW::Uncertainty":1e-05,"abrStdAW::Value":140.91,"abrStdAW::±":0.01}
{"Element":"neodymium","Symbol":"Nd","Atomic number":"60","stdAW::Value":"144.242","stdAW::Uncertainty":0.003,"abrStdAW::Value":144.24,"abrStdAW::±":0.01,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"promethium","Symbol":"Pm","Atomic number":"61","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"samarium","Symbol":"Sm","Atomic number":"62","stdAW::Value":"150.36","stdAW::Uncertainty":0.02,"abrStdAW::Value":150.36,"abrStdAW::±":0.02,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"europium","Symbol":"Eu","Atomic number":"63","stdAW::Value":"151.964","stdAW::Uncertainty":0.001,"abrStdAW::Value":151.96,"abrStdAW::±":0.01,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"gadolinium","Symbol":"Gd","Atomic number":"64","stdAW::Value":"157.25","stdAW::Uncertainty":0.03,"abrStdAW::Value":157.25,"abrStdAW::±":0.03,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"terbium","Symbol":"Tb","Atomic number":"65","stdAW::Value":"158.925354","stdAW::Uncertainty":7e-06,"abrStdAW::Value":158.93,"abrStdAW::±":0.01}
{"Element":"dysprosium","Symbol":"Dy","Atomic number":"66","stdAW::Value":"162.5","stdAW::Uncertainty":0.001,"abrStdAW::Value":162.5,"abrStdAW::±":0.01,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"holmium","Symbol":"Ho","Atomic number":"67","stdAW::Value":"164.930329","stdAW::Uncertainty":5e-06,"abrStdAW::Value":164.93,"abrStdAW::±":0.01}
{"Element":"erbium","Symbol":"Er","Atomic number":"68","stdAW::Value":"167.259","stdAW::Uncertainty":0.003,"abrStdAW::Value":167.26,"abrStdAW::±":0.01,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"thulium","Symbol":"Tm","Atomic number":"69","stdAW::Value":"168.934219","stdAW::Uncertainty":5e-06,"abrStdAW::Value":168.93,"abrStdAW::±":0.01}
{"Element":"ytterbium","Symbol":"Yb","Atomic number":"70","stdAW::Value":"173.045","stdAW::Uncertainty":0.01,"abrStdAW::Value":173.05,"abrStdAW::±":0.02,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"lutetium","Symbol":"Lu","Atomic number":"71","stdAW::Value":"174.9668","stdAW::Uncertainty":0.0001,"abrStdAW::Value":174.97,"abrStdAW::±":0.01,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"hafnium","Symbol":"Hf","Atomic number":"72","stdAW::Value":"178.486","stdAW::Uncertainty":0.006,"abrStdAW::Value":178.49,"abrStdAW::±":0.01,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"tantalum","Symbol":"Ta","Atomic number":"73","stdAW::Value":"180.94788","stdAW::Uncertainty":0.00002,"abrStdAW::Value":180.95,"abrStdAW::±":0.01}
{"Element":"tungsten","Symbol":"W","Atomic number":"74","stdAW::Value":"183.84","stdAW::Uncertainty":0.01,"abrStdAW::Value":183.84,"abrStdAW::±":0.01}
{"Element":"rhenium","Symbol":"Re","Atomic number":"75","stdAW::Value":"186.207","stdAW::Uncertainty":0.001,"abrStdAW::Value":186.21,"abrStdAW::±":0.01}
{"Element":"osmium","Symbol":"Os","Atomic number":"76","stdAW::Value":"190.23","stdAW::Uncertainty":0.03,"abrStdAW::Value":190.23,"abrStdAW::±":0.03,"Note":"Geological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"iridium","Symbol":"Ir","Atomic number":"77","stdAW::Value":"192.217","stdAW::Uncertainty":0.002,"abrStdAW::Value":192.22,"abrStdAW::±":0.01}
{"Element":"platinum","Symbol":"Pt","Atomic number":"78","stdAW::Value":"195.084","stdAW::Uncertainty":0.009,"abrStdAW::Value":195.08,"abrStdAW::±":0.02}
{"Element":"gold","Symbol":"Au","Atomic number":"79","stdAW::Value":"196.966570","stdAW::Uncertainty":4e-06,"abrStdAW::Value":196.97,"abrStdAW::±":0.01}
{"Element":"mercury","Symbol":"Hg","Atomic number":"80","stdAW::Value":"200.592","stdAW::Uncertainty":0.003,"abrStdAW::Value":200.59,"abrStdAW::±":0.01}
{"Element":"thallium","Symbol":"Tl","Atomic number":"81","stdAW::Value":"[204.382,204.385]","abrStdAW::Value":204.38,"abrStdAW::±":0.01}
{"Element":"lead","Symbol":"Pb","Atomic number":"82","stdAW::Value":"[206.14,207.94]","abrStdAW::Value":207.2,"abrStdAW::±":1.1}
{"Element":"bismuth","Symbol":"Bi","Atomic number":"83","stdAW::Value":"208.98040","stdAW::Uncertainty":1e-05,"abrStdAW::Value":208.98,"abrStdAW::±":0.01,"Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"polonium","Symbol":"Po","Atomic number":"84","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"astatine","Symbol":"At","Atomic number":"85","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"radon","Symbol":"Rn","Atomic number":"86","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"francium","Symbol":"Fr","Atomic number":"87","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"radium","Symbol":"Ra","Atomic number":"88","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"actinium","Symbol":"Ac","Atomic number":"89","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"thorium","Symbol":"Th","Atomic number":"90","stdAW::Value":"232.0377","stdAW::Uncertainty":0.0004,"abrStdAW::Value":232.04,"abrStdAW::±":0.01,"Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined.\nGeological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty."}
{"Element":"protactinium","Symbol":"Pa","Atomic number":"91","stdAW::Value":"231.03588","stdAW::Uncertainty":1e-05,"abrStdAW::Value":231.04,"abrStdAW::±":0.01,"Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"uranium","Symbol":"U","Atomic number":"92","stdAW::Value":"238.02891","stdAW::Uncertainty":0.00003,"abrStdAW::Value":238.03,"abrStdAW::±":0.01,"Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined.\nGeological and biological materials are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such materials and that given in the table may exceed the stated uncertainty.\nModified isotopic compositions may be found in commercially available material because the material has been subjected to some undisclosed or inadvertent isotopic fractionation. Substantial deviations in atomic weight of the element from that given in the table can occur."}
{"Element":"neptunium","Symbol":"Np","Atomic number":"93","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"plutonium","Symbol":"Pu","Atomic number":"94","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"americium","Symbol":"Am","Atomic number":"95","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"curium","Symbol":"Cm","Atomic number":"96","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"berkelium","Symbol":"Bk","Atomic number":"97","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"californium","Symbol":"Cf","Atomic number":"98","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"einsteinium","Symbol":"Es","Atomic number":"99","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"fermium","Symbol":"Fm","Atomic number":"100","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"mendelevium","Symbol":"Md","Atomic number":"101","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"nobelium","Symbol":"No","Atomic number":"102","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"lawrencium","Symbol":"Lr","Atomic number":"103","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"rutherfordium","Symbol":"Rf","Atomic number":"104","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"dubnium","Symbol":"Db","Atomic number":"105","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"seaborgium","Symbol":"Sg","Atomic number":"106","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"bohrium","Symbol":"Bh","Atomic number":"107","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"hassium","Symbol":"Hs","Atomic number":"108","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"meitnerium","Symbol":"Mt","Atomic number":"109","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"darmstadtium","Symbol":"Ds","Atomic number":"110","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"roentgenium","Symbol":"Rg","Atomic number":"111","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"copernicium","Symbol":"Cn","Atomic number":"112","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"nihonium","Symbol":"Nh","Atomic number":"113","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"flerovium","Symbol":"Fl","Atomic number":"114","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"moscovium","Symbol":"Mc","Atomic number":"115","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"livermorium","Symbol":"Lv","Atomic number":"116","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"tennessine","Symbol":"Ts","Atomic number":"117","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}
{"Element":"oganesson","Symbol":"Og","Atomic number":"118","Note":"Element has no stable isotope, only radioactive isotopes. For four elements (Bi, Th, Pa, and U) a standard atomic weight is tabulated because these elements have a characteristic terrestrial isotopic composition; for the other 34 elements a standard atomic weight cannot be determined."}