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Chemistry LibreTexts

2: Naming and Composition

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    329724
  • There are many substances that exist as two or more atoms connected together so strongly that they behave as a single particle. These multiatom combinations are called moleculesThe smallest part of a substance that has the physical and chemical properties of that substance.. A molecule is the smallest part of a substance that has the physical and chemical properties of that substance. In some respects, a molecule is similar to an atom. A molecule, however, is composed of more than one atom.

    • 2.1: A Molecular View of Elements and Compounds
      Most elements exist with individual atoms as their basic unit. It is assumed that there is only one atom in a formula if there is no numerical subscript on the right side of an element’s symbol. There are many substances that exist as two or more atoms connected together so strongly that they behave as a single particle. These multi-atom combinations are called molecules. The smallest part of a substance that has the physical and chemical properties of that substance.
    • 2.2: Writing Formulas for Ionic Compounds
      Formulas for ionic compounds contain the symbols and number of each atom present in a compound in the lowest whole number ratio.
    • 2.3: Nomenclature- Naming Compounds
      The primary function of chemical nomenclature is to ensure that a spoken or written chemical name leaves no ambiguity concerning which chemical compound the name refers to: each chemical name should refer to a single substance. A less important aim is to ensure that each substance has a single name, although a limited number of alternative names is acceptable in some cases. Preferably, the name also conveys some information about the structure or chemistry of a compound.
    • 2.4: Naming Ionic Compounds
      Ionic compounds are named by stating the cation first, followed by the anion. Positive and negative charges must balance. Some anions have multiple forms and are named accordingly with the use of roman numerals in parenthes. Ternary compounds are composed of three or more elements.
    • 2.5: Naming Molecular Compounds
      Molecular compounds are inorganic compounds that take the form of discrete molecules. Examples include such familiar substances as water and carbon dioxide. These compounds are very different from ionic compounds like sodium chloride. Ionic compounds are formed when metal atoms lose one or more of their electrons to nonmetal atoms. The resulting cations and anions are electrostatically attracted to each other.
    • 2.6: Naming Acids
      An acid can be defined in several ways. The most straightforward definition is that an acid is a molecular compound that contains one or more hydrogen atoms and produces hydrogen ions when dissolved in water.
    • 2.7: Nomenclature Summary
      Brief overview of chemical nomenclature.
    • 2.8: Formula Mass- The Mass of a Molecule or Formula Unit
      Formula masses of ionic compounds can be determined from the masses of the atoms in their formulas.
    • 2.9: Counting Atoms by the Gram
      In chemistry, it is impossible to deal with a single atom or molecule because we can't see them or count them or weigh them. Chemists have selected a number of particles with which to work that is convenient. Since molecules are extremely small, you may suspect this number is going to be very large and you are right. The number of particles in this group is Avagadro's number and the name of this group is the mole.
    • 2.10: Counting Molecules by the Gram
      The molecular mass of a substance is the sum of the average masses of the atoms in one molecule of a substance. Calculations for formula mass and molecular mass are described. Calculations involving conversions between moles of a material and the mass of that material are described. Calculations are illustrated for conversions between mass and number of particles.
    • 2.11: Chemical Formulas as Conversion Factors
      Using formulas to indicate how many atoms of each element we have in a substance, we can relate the number of moles of molecules to the number of moles of atoms.  In any given formula the ratio of the number of moles of molecules (or formula units) to the number of moles of atoms can be used as a conversion factor.
    • 2.12: Mass Percent Composition of Compounds
      Chemists often need to know what elements are present in a compound and in what percentage. The percent composition is the percent by mass of each element in a compound.
    • 2.13: Mass Percent Composition from a Chemical Formula
      he percent composition of a compound can also be determined from the formula of the compound. The subscripts in the formula are first used to calculate the mass of each element in one mole of the compound. That is divided by the molar mass of the compound and multiplied by 100%.
    • 2.14: Calculating Empirical Formulas for Compounds
      An empirical formula tells us the relative ratios of different atoms in a compound. The ratios hold true on the molar level as well. A process is described for the calculation of the empirical formula for a compound based on the percent composition of that compound.
    • 2.15: Calculating Molecular Formulas for Compounds
      A procedure is described that allows the calculation of the exact molecular formula for a compound.

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