Ionic and Covalent bonding David A. Katz Pima Community College Tucson, AZ

Ionic Bonding Between a metal with low ionization energy ( little energy required to remove an electron) and a non-metal with high electronegativity and electron affinity ( wants to grab an electron towards it)

Formation of NaCl

Lewis Structures for Ionic Compounds Ba • O •• •• O Ba 2+ 2- BaO Mg • Cl •• •• Cl Mg 2+ - 2 MgCl2 Binary ionic compounds. Note the types of arrows used to move electrons – fishhooks for single e-. Write the Lewis symbol for each atom Determine how many e- each atom must gain or lose. Use multiples of one or both ions to balance the number of electrons.

Properties of Ionic Compounds Held together by strong electrostatic forces Opposite charges attract High melting points and boiling points Regular structures – giant ionic lattices When melted or dissolved ionic compounds conduct electricity

Dissolving in Water

conductivity

Covalent Bond Between two elements with high ionization energy ( do not give up electrons easily) and high electronegativity ( try to grab the electron to each of them) Here neither atom is willing to give up its electron Instead the nuclei share the electrons between them

Lewis Structures Lewis structures are representations of molecules showing all electrons, bonding and non-bonding Example : Li2 O

Lewis structures F2 C2H6

Multiple Covalent bonds More than one pair of electrons can be shared between the same atoms O2 N2

Properties of Covalent Molecules Contain non-metals Weak bonds Valence electrons are shared between atoms Polar molecules dissolve in polar solvents Volatile Low melting and boiling points Insoluble in water Non polar compounds do not conduct electricity; polar compounds can conduct small amounts of electricity