Part One I › Division II II › Section 121 121

Chemical Elements; Periodic Variation in Their Properties

Subject Outline

AThe systematic classification of the elements on the basis of their chemical and physical properties and atomic structures: the periodic law of the elements
BThe groups of the chemical elements in the long form of the periodic table: their occurrence, history, physical and chemical properties, principal compounds, production, and uses
- 1Hydrogen, its forms, isotopes, and compounds: water, its structure, forms, and physical and chemical properties
- 2The alkali metals, or the Group la elements of the periodic table: lithium, sodium, potassium, rubidium, cesium, francium
- 3The alkaline-earth metals, or the Group Ila elements of the periodic table: beryllium, magnesium, calcium, strontium, barium, radium
- 4The boron group of the elements, or the Group Ilia elements of the periodic table: boron, aluminum, gallium, indium, thallium
- 5The carbon group of the elements, or the Group IVa elements of the periodic table: carbon, silicon, germanium, tin, lead
- 6The nitrogen group of the elements, or the Group Va elements of the periodic table: nitrogen, phosphorus, arsenic, antimony, bismuth
- 7The oxygen group of the elements, or the Group Via elements of the periodic table: oxygen, sulfur, selenium, tellurium, polonium
- 8The halogen elements, or the Group Vila elements of the periodic table: fluorine, chlorine, bromine, iodine, astatine
- 9The noble gases, or the Group 0 elements of the periodic table, formerly called the inert gases: helium, neon, argon, krypton, xenon, radon
- 10The zinc group elements, or the Group lib elements of the periodic table: zinc, cadmium, mercury
- 11The transition elements: elements with partly filled d or /orbitals occupying the middle portion of the periodic table
  - aIndividual elements of the first transition series: titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper
  - bIndividual elements of the second and third transition series: zirconium and hafnium, niobium and tantalum, molybdenum and tungsten, technetium and rhenium, ruthenium and osmium, rhodium and iridium, palladium and platinum, silver and gold
  - cThe lanthanide elements [see B.12., below]
  - dThe actinide elements [see B.13., below]
- 12The rare-earth, or lanthanide, elements of the periodic table: scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium [see also 724.C.3.U.]
- 13The actinide elements of the periodic table: actinium, thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, lawrencium
- 14The transactinide elements of the periodic table: unnilquadium (or rutherfordium), unnilpentium (or hahnium), unnilhexium, unnilseptium, unniloctium, unnilennium; heavier elements which have yet to be discovered but whose existence is extrapolated based on the periodic law
COther classifications of the elements or groups of them
- 1Metals; semimetals, or metalloids; nonmetals
- 2Stable and radioactive elements
- 3Native and combined elements
- 4Noble metals, including the platinum group of metals
- 5Synthetic elements: transuranium elements
- 6Biologically active or essential elements [see 335.A.3.]
- 7Technologically significant elements [see 724.C.3.]
DThe origin of the elements and their relative abundances in nature
- 1On Earth
  - aIn the crust [see also 214.C.]
  - bIn the hydrosphere [see also 222.B. and C.]
  - cIn the atmosphere [see also 221.A.1.]
  - dIn the biosphere
- 2In the solar system [see also 133.A.]
- 3In the stars [see also 132.D.7.b.]