<descriptor thcode="2"><thesaurus thcode="2" name="USGS Thesaurus" scope="Topics and methods of scientific study carried out by USGS, with product types, scientific disciplines, geologic time, and types of institutional structure and activities.  Broad and shallow, used to help people find scientific information." creator="U.S. Geological Survey" rights="Public domain" edition="2.0" date="2020-01-09" codetype="number" prefix="topic" uri="https://www2.usgs.gov/science/USGSThesaurus" tblname="term" nonpref="nonpref" relterm="relterm" root_code="1" contact="pschweitzer"><category><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/></category><altlabel><altlabel>USGSThesaurus</altlabel><altlabel>USGSThesaurus</altlabel></altlabel></thesaurus><term thcode="2" code="1427" name="chemical elements" parent="1382" scope="Chemical substances distinguished by atomic number. http://periodic.lanl.gov/"/><bt><term thcode="2" code="1382" name="elements" parent="1174" scope="Chemical elements and element groups"/><term thcode="2" code="1174" name="topics" parent="1" scope="Themes, subjects, and concerns for which USGS information resources are relevant."/><term thcode="2" code="1" name="Categories" scope="Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."/></bt><nt><term thcode="2" code="1385" name="actinium" parent="1427" scope="Rare earth (actinide series) element with symbol Ac and atomic number 89 &lt;http://periodic.lanl.gov/89.shtml&gt;"/><term thcode="2" code="1390" name="aluminum" parent="1427" scope="Metalloid element with symbol Al and atomic number 13 &lt;http://periodic.lanl.gov/13.shtml&gt;"/><term thcode="2" code="1392" name="americium" parent="1427" scope="Rare earth (actinide series) element with symbol Am and atomic number 95 &lt;http://periodic.lanl.gov/95.shtml&gt;"/><term thcode="2" code="1393" name="antimony" parent="1427" scope="Metalloid element with symbol Sb and atomic number 51 &lt;http://periodic.lanl.gov/51.shtml&gt;"/><term thcode="2" code="1395" name="argon" parent="1427" scope="Noble gas element with symbol Ar and atomic number 18 &lt;http://periodic.lanl.gov/18.shtml&gt;"/><term thcode="2" code="1396" name="arsenic" parent="1427" scope="Nonmetal element with symbol As and atomic number 33 &lt;http://periodic.lanl.gov/33.shtml&gt;"/><term thcode="2" code="1398" name="astatine" parent="1427" scope="Halogen element with symbol At and atomic number 85 &lt;http://periodic.lanl.gov/85.shtml&gt;"/><term thcode="2" code="1403" name="barium" parent="1427" scope="Alkaline earth element with symbol Ba and atomic number 56 &lt;http://periodic.lanl.gov/56.shtml&gt;"/><term thcode="2" code="1405" name="berkelium" parent="1427" scope="Rare earth (actinide series) element with symbol Bk and atomic number 97 &lt;http://periodic.lanl.gov/97.shtml&gt;"/><term thcode="2" code="1406" name="beryllium" parent="1427" scope="Alkaline earth element with symbol Be and atomic number 4 &lt;http://periodic.lanl.gov/4.shtml&gt;"/><term thcode="2" code="1409" name="bismuth" parent="1427" scope="Metalloid element with symbol Bi and atomic number 83 &lt;http://periodic.lanl.gov/83.shtml&gt;"/><term thcode="2" code="1411" name="bohrium" parent="1427" scope="Metal element with symbol Bh and atomic number 107 &lt;http://periodic.lanl.gov/107.shtml&gt;"/><term thcode="2" code="1412" name="boron" parent="1427" scope="Nonmetal element with symbol B and atomic number 5 &lt;http://periodic.lanl.gov/5.shtml&gt;"/><term thcode="2" code="1414" name="bromine" parent="1427" scope="Halogen element with symbol Br and atomic number 35 &lt;http://periodic.lanl.gov/35.shtml&gt;"/><term thcode="2" code="1417" name="cadmium" parent="1427" scope="Metal element with symbol Cd and atomic number 48 &lt;http://periodic.lanl.gov/48.shtml&gt;"/><term thcode="2" code="1418" name="calcium" parent="1427" scope="Alkaline earth element with symbol Ca and atomic number 20 &lt;http://periodic.lanl.gov/20.shtml&gt;"/><term thcode="2" code="1419" name="californium" parent="1427" scope="Rare earth (actinide series) element with symbol Cf and atomic number 98 &lt;http://periodic.lanl.gov/98.shtml&gt;"/><term thcode="2" code="1420" name="carbon" parent="1427" scope="Nonmetal element with symbol C and atomic number 6 &lt;http://periodic.lanl.gov/6.shtml&gt;"/><term thcode="2" code="1423" name="cerium" parent="1427" scope="Rare earth (lanthanide series) element with symbol Ce and atomic number 58 &lt;http://periodic.lanl.gov/58.shtml&gt;"/><term thcode="2" code="1424" name="cesium" parent="1427" scope="Alkali metal element with symbol Cs and atomic number 55 &lt;http://periodic.lanl.gov/55.shtml&gt;"/><term thcode="2" code="1428" name="chlorine" parent="1427" scope="Halogen element with symbol Cl and atomic number 17 &lt;http://periodic.lanl.gov/17.shtml&gt;"/><term thcode="2" code="1429" name="chromium" parent="1427" scope="Metal element with symbol Cr and atomic number 24 &lt;http://periodic.lanl.gov/24.shtml&gt;"/><term thcode="2" code="1433" name="cobalt" parent="1427" scope="Metal element with symbol Co and atomic number 27 &lt;http://periodic.lanl.gov/27.shtml&gt;"/><term thcode="2" code="1434" name="copper" parent="1427" scope="Metal element with symbol Cu and atomic number 29 &lt;http://periodic.lanl.gov/29.shtml&gt;"/><term thcode="2" code="1438" name="curium" parent="1427" scope="Rare earth (actinide series) element with symbol Cm and atomic number 96 &lt;http://periodic.lanl.gov/96.shtml&gt;"/><term thcode="2" code="1439" name="darmstadtium" parent="1427" scope="Metal element with symbol Ds and atomic number 110 &lt;http://periodic.lanl.gov/110.shtml&gt;"/><term thcode="2" code="1442" name="dubnium" parent="1427" scope="Metal element with symbol Db and atomic number 105 &lt;http://periodic.lanl.gov/105.shtml&gt;"/><term thcode="2" code="1444" name="dysprosium" parent="1427" scope="Rare earth (lanthanide series) element with symbol Dy and atomic number 66 &lt;http://periodic.lanl.gov/66.shtml&gt;"/><term thcode="2" code="1445" name="einsteinium" parent="1427" scope="Rare earth (actinide series) element with symbol Es and atomic number 99 &lt;http://periodic.lanl.gov/99.shtml&gt;"/><term thcode="2" code="1447" name="erbium" parent="1427" scope="Rare earth (lanthanide series) element with symbol Er and atomic number 68 &lt;http://periodic.lanl.gov/68.shtml&gt;"/><term thcode="2" code="1450" name="europium" parent="1427" scope="Rare earth (lanthanide series) element with symbol Eu and atomic number 63 &lt;http://periodic.lanl.gov/63.shtml&gt;"/><term thcode="2" code="1453" name="fermium" parent="1427" scope="Rare earth (actinide series) element with symbol Fm and atomic number 100 &lt;http://periodic.lanl.gov/100.shtml&gt;"/><term thcode="2" code="1454" name="fluorine" parent="1427" scope="Halogen element with symbol F and atomic number 9 &lt;http://periodic.lanl.gov/9.shtml&gt;"/><term thcode="2" code="1457" name="francium" parent="1427" scope="Alkali metal element with symbol Fr and atomic number 87 &lt;http://periodic.lanl.gov/87.shtml&gt;"/><term thcode="2" code="1459" name="gadolinium" parent="1427" scope="Rare earth (lanthanide series) element with symbol Gd and atomic number 64 &lt;http://periodic.lanl.gov/64.shtml&gt;"/><term thcode="2" code="1460" name="gallium" parent="1427" scope="Metalloid element with symbol Ga and atomic number 31 &lt;http://periodic.lanl.gov/31.shtml&gt;"/><term thcode="2" code="1463" name="germanium" parent="1427" scope="Metalloid element with symbol Ge and atomic number 32 &lt;http://periodic.lanl.gov/32.shtml&gt;"/><term thcode="2" code="1464" name="gold" parent="1427" scope="Metal element with symbol Au and atomic number 79 &lt;http://periodic.lanl.gov/79.shtml&gt;"/><term thcode="2" code="1466" name="hafnium" parent="1427" scope="Metal element with symbol Hf and atomic number 72 &lt;http://periodic.lanl.gov/72.shtml&gt;"/><term thcode="2" code="1468" name="hassium" parent="1427" scope="Metal element with symbol Hs and atomic number 108 &lt;http://periodic.lanl.gov/108.shtml&gt;"/><term thcode="2" code="1470" name="helium" parent="1427" scope="Noble gas element with symbol He and atomic number 2 &lt;http://periodic.lanl.gov/2.shtml&gt;"/><term thcode="2" code="1474" name="holmium" parent="1427" scope="Rare earth (lanthanide series) element with symbol Ho and atomic number 67 &lt;http://periodic.lanl.gov/67.shtml&gt;"/><term thcode="2" code="1476" name="hydrogen" parent="1427" scope="Alkali metal element with symbol H and atomic number 1 &lt;http://periodic.lanl.gov/1.shtml&gt;"/><term thcode="2" code="1479" name="indium" parent="1427" scope="Metalloid element with symbol In and atomic number 49 &lt;http://periodic.lanl.gov/49.shtml&gt;"/><term thcode="2" code="1481" name="iodine" parent="1427" scope="Halogen element with symbol I and atomic number 53 &lt;http://periodic.lanl.gov/53.shtml&gt;"/><term thcode="2" code="1484" name="iridium" parent="1427" scope="Metal element with symbol Ir and atomic number 77 &lt;http://periodic.lanl.gov/77.shtml&gt;"/><term thcode="2" code="1483" name="iron" parent="1427" scope="Metal element with symbol Fe and atomic number 26 &lt;http://periodic.lanl.gov/26.shtml&gt;"/><term thcode="2" code="1487" name="krypton" parent="1427" scope="Noble gas element with symbol Kr and atomic number 36 &lt;http://periodic.lanl.gov/36.shtml&gt;"/><term thcode="2" code="1490" name="lanthanum" parent="1427" scope="Rare earth (lanthanide series) element with symbol La and atomic number 57 &lt;http://periodic.lanl.gov/57.shtml&gt;"/><term thcode="2" code="1491" name="lawrencium" parent="1427" scope="Rare earth (actinide series) element with symbol Lr and atomic number 103 &lt;http://periodic.lanl.gov/103.shtml&gt;"/><term thcode="2" code="1492" name="lead" parent="1427" scope="Metalloid element with symbol Pb and atomic number 82 &lt;http://periodic.lanl.gov/82.shtml&gt;"/><term thcode="2" code="1494" name="lithium" parent="1427" scope="Alkali metal element with symbol Li and atomic number 3 &lt;http://periodic.lanl.gov/3.shtml&gt;"/><term thcode="2" code="1497" name="lutetium" parent="1427" scope="Rare earth (lanthanide series) element with symbol Lu and atomic number 71 &lt;http://periodic.lanl.gov/71.shtml&gt;"/><term thcode="2" code="1498" name="magnesium" parent="1427" scope="Alkaline earth element with symbol Mg and atomic number 12 &lt;http://periodic.lanl.gov/12.shtml&gt;"/><term thcode="2" code="1499" name="manganese" parent="1427" scope="Metal element with symbol Mn and atomic number 25 &lt;http://periodic.lanl.gov/25.shtml&gt;"/><term thcode="2" code="1501" name="meitnerium" parent="1427" scope="Metal element with symbol Mt and atomic number 109 &lt;http://periodic.lanl.gov/109.shtml&gt;"/><term thcode="2" code="1502" name="mendelevium" parent="1427" scope="Rare earth (actinide series) element with symbol Md and atomic number 101 &lt;http://periodic.lanl.gov/101.shtml&gt;"/><term thcode="2" code="1503" name="mercury" parent="1427" scope="Metal element with symbol Hg and atomic number 80 &lt;http://periodic.lanl.gov/80.shtml&gt;"/><term thcode="2" code="1509" name="molybdenum" parent="1427" scope="Metal element with symbol Mo and atomic number 42 &lt;http://periodic.lanl.gov/42.shtml&gt;"/><term thcode="2" code="1516" name="neodymium" parent="1427" scope="Rare earth (lanthanide series) element with symbol Nd and atomic number 60 &lt;http://periodic.lanl.gov/60.shtml&gt;"/><term thcode="2" code="1517" name="neon" parent="1427" scope="Noble gas element with symbol Ne and atomic number 10 &lt;http://periodic.lanl.gov/10.shtml&gt;"/><term thcode="2" code="1518" name="neptunium" parent="1427" scope="Rare earth (actinide series) element with symbol Np and atomic number 93 &lt;http://periodic.lanl.gov/93.shtml&gt;"/><term thcode="2" code="1520" name="nickel" parent="1427" scope="Metal element with symbol Ni and atomic number 28 &lt;http://periodic.lanl.gov/28.shtml&gt;"/><term thcode="2" code="1521" name="niobium" parent="1427" scope="Metal element with symbol Nb and atomic number 41 &lt;http://periodic.lanl.gov/41.shtml&gt;"/><term thcode="2" code="1522" name="nitrogen" parent="1427" scope="Nonmetal element with symbol N and atomic number 7 &lt;http://periodic.lanl.gov/7.shtml&gt;"/><term thcode="2" code="1524" name="nobelium" parent="1427" scope="Rare earth (actinide series) element with symbol No and atomic number 102 &lt;http://periodic.lanl.gov/102.shtml&gt;"/><term thcode="2" code="1530" name="osmium" parent="1427" scope="Metal element with symbol Os and atomic number 76 &lt;http://periodic.lanl.gov/76.shtml&gt;"/><term thcode="2" code="1531" name="oxygen" parent="1427" scope="Nonmetal element with symbol O and atomic number 8 &lt;http://periodic.lanl.gov/8.shtml&gt;"/><term thcode="2" code="1534" name="palladium" parent="1427" scope="Metal element with symbol Pd and atomic number 46 &lt;http://periodic.lanl.gov/46.shtml&gt;"/><term thcode="2" code="1537" name="phosphorus" parent="1427" scope="Nonmetal element with symbol P and atomic number 15 &lt;http://periodic.lanl.gov/15.shtml&gt;"/><term thcode="2" code="1538" name="platinum" parent="1427" scope="Metal element with symbol Pt and atomic number 78 &lt;http://periodic.lanl.gov/78.shtml&gt;"/><term thcode="2" code="1539" name="plutonium" parent="1427" scope="Rare earth (actinide series) element with symbol Pu and atomic number 94 &lt;http://periodic.lanl.gov/94.shtml&gt;"/><term thcode="2" code="1542" name="polonium" parent="1427" scope="Metalloid element with symbol Po and atomic number 84 &lt;http://periodic.lanl.gov/84.shtml&gt;"/><term thcode="2" code="1543" name="potassium" parent="1427" scope="Alkali metal element with symbol K and atomic number 19 &lt;http://periodic.lanl.gov/19.shtml&gt;"/><term thcode="2" code="1545" name="praseodymium" parent="1427" scope="Rare earth (lanthanide series) element with symbol Pr and atomic number 59 &lt;http://periodic.lanl.gov/59.shtml&gt;"/><term thcode="2" code="1546" name="promethium" parent="1427" scope="Rare earth (lanthanide series) element with symbol Pm and atomic number 61 &lt;http://periodic.lanl.gov/61.shtml&gt;"/><term thcode="2" code="1547" name="protactinium" parent="1427" scope="Rare earth (actinide series) element with symbol Pa and atomic number 91 &lt;http://periodic.lanl.gov/91.shtml&gt;"/><term thcode="2" code="1551" name="radium" parent="1427" scope="Alkaline earth element with symbol Ra and atomic number 88 &lt;http://periodic.lanl.gov/88.shtml&gt;"/><term thcode="2" code="1552" name="radon" parent="1427" scope="Noble gas element with symbol Rn and atomic number 86 &lt;http://periodic.lanl.gov/86.shtml&gt;"/><term thcode="2" code="1558" name="rhenium" parent="1427" scope="Metal element with symbol Re and atomic number 75 &lt;http://periodic.lanl.gov/75.shtml&gt;"/><term thcode="2" code="1559" name="rhodium" parent="1427" scope="Metal element with symbol Rh and atomic number 45 &lt;http://periodic.lanl.gov/45.shtml&gt;"/><term thcode="2" code="1562" name="rubidium" parent="1427" scope="Alkali metal element with symbol Rb and atomic number 37 &lt;http://periodic.lanl.gov/37.shtml&gt;"/><term thcode="2" code="1563" name="ruthenium" parent="1427" scope="Metal element with symbol Ru and atomic number 44 &lt;http://periodic.lanl.gov/44.shtml&gt;"/><term thcode="2" code="1564" name="rutherfordium" parent="1427" scope="Metal element with symbol Rf and atomic number 104 &lt;http://periodic.lanl.gov/104.shtml&gt;"/><term thcode="2" code="1566" name="samarium" parent="1427" scope="Rare earth (lanthanide series) element with symbol Sm and atomic number 62 &lt;http://periodic.lanl.gov/62.shtml&gt;"/><term thcode="2" code="1569" name="scandium" parent="1427" scope="Metal element with symbol Sc and atomic number 21 &lt;http://periodic.lanl.gov/21.shtml&gt;"/><term thcode="2" code="1571" name="seaborgium" parent="1427" scope="Metal element with symbol Sg and atomic number 106 &lt;http://periodic.lanl.gov/106.shtml&gt;"/><term thcode="2" code="1572" name="selenium" parent="1427" scope="Nonmetal element with symbol Se and atomic number 34 &lt;http://periodic.lanl.gov/34.shtml&gt;"/><term thcode="2" code="1575" name="silicon" parent="1427" scope="Nonmetal element with symbol si and atomic number 14 &lt;http://periodic.lanl.gov/14.shtml&gt;"/><term thcode="2" code="1576" name="silver" parent="1427" scope="Metal element with symbol Ag and atomic number 47 &lt;http://periodic.lanl.gov/47.shtml&gt;"/><term thcode="2" code="1579" name="sodium" parent="1427" scope="Alkali metal element with symbol Na and atomic number 11 &lt;http://periodic.lanl.gov/11.shtml&gt;"/><term thcode="2" code="1581" name="strontium" parent="1427" scope="Alkaline earth element with symbol Sr and atomic number 38 &lt;http://periodic.lanl.gov/38.shtml&gt;"/><term thcode="2" code="1582" name="sulfur" parent="1427" scope="Nonmetal element with symbol S and atomic number 16 &lt;http://periodic.lanl.gov/16.shtml&gt;"/><term thcode="2" code="1584" name="tantalum" parent="1427" scope="Metal element with symbol Ta and atomic number 73 &lt;http://periodic.lanl.gov/73.shtml&gt;"/><term thcode="2" code="1588" name="technetium" parent="1427" scope="Metal element with symbol Tc and atomic number 43 &lt;http://periodic.lanl.gov/43.shtml&gt;"/><term thcode="2" code="1589" name="tellurium" parent="1427" scope="Nonmetal element with symbol Te and atomic number 52 &lt;http://periodic.lanl.gov/52.shtml&gt;"/><term thcode="2" code="1590" name="terbium" parent="1427" scope="Rare earth (lanthanide series) element with symbol Tb and atomic number 65 &lt;http://periodic.lanl.gov/65.shtml&gt;"/><term thcode="2" code="1592" name="thallium" parent="1427" scope="Metalloid element with symbol Tl and atomic number 81 &lt;http://periodic.lanl.gov/81.shtml&gt;"/><term thcode="2" code="1593" name="thorium" parent="1427" scope="Rare earth (actinide series) element with symbol Th and atomic number 90 &lt;http://periodic.lanl.gov/90.shtml&gt;"/><term thcode="2" code="1594" name="thulium" parent="1427" scope="Rare earth (lanthanide series) element with symbol Tm and atomic number 69 &lt;http://periodic.lanl.gov/69.shtml&gt;"/><term thcode="2" code="1596" name="tin" parent="1427" scope="Metalloid element with symbol Sn and atomic number 50 &lt;http://periodic.lanl.gov/50.shtml&gt;"/><term thcode="2" code="1597" name="titanium" parent="1427" scope="Metal element with symbol Ti and atomic number 22 &lt;http://periodic.lanl.gov/22.shtml&gt;"/><term thcode="2" code="1600" name="tungsten" parent="1427" scope="Metal element with symbol W and atomic number 74 &lt;http://periodic.lanl.gov/74.shtml&gt;"/><term thcode="2" code="1602" name="ununnilium" parent="1427" scope="Metal element with symbol Uuu and atomic number 111 &lt;http://periodic.lanl.gov/111.shtml&gt;"/><term thcode="2" code="1603" name="ununnubium" parent="1427" scope="Metal element with symbol Uub and atomic number 113 &lt;http://periodic.lanl.gov/113.shtml&gt;"/><term thcode="2" code="1604" name="ununnunium" parent="1427" scope="Metal element with symbol Uun and atomic number 112 &lt;http://periodic.lanl.gov/112.shtml&gt;"/><term thcode="2" code="1605" name="uranium" parent="1427" scope="Rare earth (actinide series) element with symbol U and atomic number 92 &lt;http://periodic.lanl.gov/92.shtml&gt;"/><term thcode="2" code="1610" name="vanadium" parent="1427" scope="Metal element with symbol V and atomic number 23 &lt;http://periodic.lanl.gov/23.shtml&gt;"/><term thcode="2" code="1613" name="xenon" parent="1427" scope="Noble gas element with symbol Xe and atomic number 54 &lt;http://periodic.lanl.gov/54.shtml&gt;"/><term thcode="2" code="1616" name="ytterbium" parent="1427" scope="Rare earth (lanthanide series) element with symbol Yb and atomic number 70 &lt;http://periodic.lanl.gov/70.shtml&gt;"/><term thcode="2" code="1617" name="yttrium" parent="1427" scope="Metal element with symbol Y and atomic number 39 &lt;http://periodic.lanl.gov/39.shtml&gt;"/><term thcode="2" code="1618" name="zinc" parent="1427" scope="Metal element with symbol Zn and atomic number 30 &lt;http://periodic.lanl.gov/30.shtml&gt;"/><term thcode="2" code="1619" name="zirconium" parent="1427" scope="Metal element with symbol Zr and atomic number 40 &lt;http://periodic.lanl.gov/40.shtml&gt;"/></nt></descriptor>