Fundamentals of ChemistryDOE-HDBK-1015/1-93CHARACTERISTICS OF ATOMSRev. 0CH-01Page 7TABLE 2 (Cont.)Table of ElementsName and SymbolNumberWeightNameNumberWeightAtomicAtomicAtomicAtomic(amu)(amu)Thallium Tl 81204.37VanadiumV 2350.942Thorium Th 90232.03XenonXe 54131.30Thulium Tm 69168.93YtterbiumYb 70173.04Tin Sn 50118.69YttriumY 3988.905Titanium Ti 2247.90ZincZn 3065.37Tungsten W 74183.85ZirconiumZr 4091.22Uranium U92238.03MoleculesMoleculesare groups or clusters of atoms held together by means of chemical bonding. Thereare two types of molecule; molecules of an element and molecules of a compound.MoleculesofanElementIn certain cases, two single atoms of an element can be attracted to one another by abond to form a molecule. Examples of this are hydrogen, oxygen, and bromine. Themolecular formulas for these are H , O , and Br . Most gaseous elements exist as2 2 2molecules of two atoms.MoleculesofaCompoundTwo atoms of different elements held together by a bond form a compound. Themolecule is the primary particle of a chemical compound. Some examples of this type ofmolecule include hydrogen chloride (HCl), water (H O), methane (CH ), and2 4ammonia (NH ).3MolecularWeightThe weight of a molecule, the molecular weight, is the total mass of the individualatoms. Therefore, it is fairly simple to calculate the mass of any molecule if its formulais known (that is, the elements and the number of each that make up the molecule). Notethat the terms mass and weight are used interchangeably in chemistry.
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