ionic and covalent bond + lewis structure

• atoms seldom exist as independent particles in nature
• most atoms are found combined with other atoms to form molecules or giant structures called crystals.
• an atom is electrically neutral because there are equal numbers of positive charges (protons) and negative charges (electrons).
• when atoms bond, their valence electrons are distributed to stabilize the atoms
• ionic bonding - electrical attraction between large numbers of cations and anions
• covalent bonding - sharing of electrons between two atoms
• ionic bonding is metal + nonmetal
• covalent bonding is nonmetal + nonmetal
• covalent molecular compounds and nonmetallic elements of the same structure have low melting and boiling points and are nonconductors of electricity
• ions are electrically charged atoms
• ionic compounds

  1. high and low melting and boiling points
  2. solid state = non conductors , aqueous solution = conductors
  3. consists of cations and anions
  4. formed by attraction of oppositely charged ions
• noble gases are unreactive, stable, and have complete s and p orbitals
• octet rule was discovered by gilbert n. lewis
• 1. metals lose electrons due to low ionization energy
  2. nonmetals gain electrons due to high electron affinity
• lewis structure was named after gilbert n. lewis and it indicates the number of electrons in an atom
• single covalent bond has a bonding pair
• bond length - distance between the nuclei of 2 bonded atoms
• bond length decreases as the number of shared electrons increases
• triple bond has the shortest bond length
• single bond has the longest bond length
• Ionic bond


  The electrostatic attraction that holds together oppositely charged ions in a solid compound
• Ionic compounds


  • Generally are solids which have high melting and boiling points
  • In the solid state, they do not conduct electricity
  • In the molten or liquid state and in aqueous solutions, they are conductors of electricity
• Octet rule


  Atoms tend to gain, lose or share electrons until they are surrounded by eight valence electrons
• Lewis or electron dot structure

  Indicates the number of valence electrons in the atom
• Covalent molecular structure


  The combination of two nonmetals produces a compound with this structure
• Covalent molecular compounds


  Compounds consisting of molecules wherein atoms are joined by covalent bonds
• Covalent bond


  Formed by the sharing of electrons between atoms
• Lone pairs or nonbonding pairs

  Pairs of unshared electrons
• Bond length


  The distance between the nuclei of the two bonded atoms
• Writing Lewis structures of covalent molecular compounds

  1. Determine the total number of valence electrons in the compound

  2. Write the atoms in the order in which they are bonded to one another

  3. Distribute the electrons in pairs, first between each pair of bonded atoms and then around each atom to complete each of their octets
• Naming binary molecular compounds


  1. Write the name of the leftmost element in the chemical formula first

  2. The second element should be given an -ide ending

  3. Use Greek prefixes to indicate the number of atoms of each element