Chemical Formulas and Bonding

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Chemical Formulas and Bonding
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Diagrams

• Lewis dot diagrams
• Dots are used to represent valence shell
  electrons
• Electrons are placed according to Hunds rule
• Paired dots represent electron pairs
• Lewis structures
• Shared electron pairs are represented with a dash
• The number of dashes represent the number of
  shared pairs
• Unshared pairs are either represented as dots or
  not at all

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Ions

• Ions are charged particles
• Positively charged particles are cations
• Negatively charged particles are anions
• Atoms gain or lose electrons in order to attain a
  full valence shell
• Octet rule
• 2-8-8

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Ionic bonds

• Binary ionic compounds have only two types of
  atoms
• Polyatomic ions are covalently bonded atoms that
  have a net charge
• Formula units are written as Empirical Formulas
  that show the minimum ratio of ions needed to
  make a neutral compound
• Cation followed by anion
• Ions that have a variety of charges are denoted
  with Roman numbers
• The roman number denotes the ions charge

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Hydrates

• An Ionic bond that holds water within its
  crystalline structure is a hydrate
• The ionic portion is named normally
• The amount of water is denoted as a coefficient
  in front of water
• The coefficient is stated with a prefix followed
  by the word hydrate (meaning water)
• Anhydrous compounds have no water

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Acids

• Acids are nearly ionic
• Acids contain hydrogen and a typical anion
• Acids are named with respect to the anion

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Covalent Bonds

• Sharing valence shell electrons
• Attempting to have a complete octet (or full
  energy level)
• Covalently bonded compounds are molecules
• Composition of molecules is given by the
  molecular formula
• Single double and triple bonds reflect the number
  of electron pairs being shared

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Polarity

• Any charge associated with direction is said to
  be polar
• An uneven distribution of electrons creates and
  uneven distribution of charge
• Uneven distribution of charge can be calculated
  as the difference in electronegativity
• A difference in electronegativity creates a
  dipole
• A net dipole means the molecule is polar
• No net dipole is nonpolar

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Oxidation numbers

• Pure element0
• Sum of a neutral compound 0
• F is usually -1
• O is usually -2, but can be 1 as a peroxide or
  even when with a halogen
• H is 1 whenever its combined with an more
  electronegative element, -1 when with a metal
• Sum of polyatomic ion charge of ion
• Number of ion ionization number