Chemistry 5: Chemical Names and Formulas

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Chemistry 5 Chemical Names and Formulas

• Christopher Chui

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Chemical Formulas

• The most common source for the name of an element
  is some property the element exhibits
• A symbol may be used in place of the name of an
  element
• The first letter of a symbol is always
  capitalized
• Symbols consist of one, two, or three letters
• Chemical formulas indicate the relative number of
  atoms of each element present in a compound
• The structural formula for an organic compound
  can be used to determine its molecular formula

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Some Common Compounds

• Ammonia NH3
• Rust Fe2O3
• Sucrose C12H22O11
• Table salt NaCl
• Water H2O
• Acetic acid CH3COOH

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Oxidation Number

• An ion is a charged atom or group of charged
  atoms
• The charge on a single atom is called its
  oxidation number
• A monatomic ion consists of one atom of an
  element
• Ionic compounds are composed of charged particles
• Molecular compounds are composed of neutral
  particles
• Polyatomic ions consist of two or more atoms

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Oxidation Numbers of Some Monatomic Ions

• 1 H, Li, K, Ag, Na
• 2 Ba2, Cd2, Ca2, Co2, Cu2, Fe2, Pb2,
  Mg2, Mn2, Hg2, Ni2, Sr2, Sn2, Zn2
• 3 Al3, Cr3, Fe3
• 4 Pb4
• 1- Br-, Cl-, F-, H-, I-
• 2- O2-, S2-

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Oxidation Numbers of Some Polyatomic Ions

• 1 NH4
• 2 Hg22
• 1- CH3COO-, ClO3-, ClO2-, CN-, OH-, ClO-, IO3-,
  NO3- , NO2-, ClO4-, MnO4-, H2PO4-, HSO3-
• 2- CO32-, CrO42-, Cr2O72-, C2O42-, O22-,
  SiO32-, SO42- , SO32-, C4H4O62-, B4O72-, S2O32-
• 3- PO43-, PO33-

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Naming Compounds

• Roman numerals are used in naming compounds that
  contain elements with more than one oxidation
  number
• mono-, di-, tri-, tetra-, penta-, hexa-, hepta-,
  octa-
• Some compounds have names ending in ide and are
  not binary
• In naming compounds containing polyatomic ions,
  the name of the polyatomic ion is not changed
• Negative polyatomic ions that contain oxygen
  except OH- and peroxide, O2 2- have the ending
  ite or ate
• Carbon atoms can link together in chains or rings

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Formulas and Names

• Al2S3 CaBr2 H2O H2Se
• N2O NO N2O3 NO2
• N2O5 Cu2S CuS SO2
• SO3 CS2 CO CO2
• CCl4 SF6 AlAsO4 CuSO4
• (NH4)2SO4 Ni(OH)2 Cr2(C2O4)3
• ZnCO3 CH3COOH (COOH)2
• H2CO3 HCl HNO3 HClO4
• H2SO4

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Hydrocarbon Naming

• No of C-atoms Prefix
• 1 meth-
• 2 eth-
• 3 prop-
• 4 but-
• 5 pent-
• 6 hex-
• 7 hept-
• 8 oct-
• 9 non-
• 10 dec-

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Molecular and Empirical Formulas

• A molecular formula describes the composition of
  a molecule
• An empirical formula indicates the simplest
  whole-number ratio of atoms or ions in a compound
• A molecular formula is a whole-number multiple of
  an empirical formula
• Coefficients are used to represent the number of
  formula units

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Acids

• Acids give off hydrogen ions when dissolved in
  water
• Several common acids HCl, H2SO3, H2SO4, HNO3,
  CH3COOH, H3PO4

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Notes to Name Compounds

• In an ionic compound, the net charge is zero
• An ide ending indicates a binary compound
• An ite or ate ending means a polyatomic ion
• Prefixes in the name indicate a molecular
  compound
• A Roman numeral shows the ionic charge of the
  cation