Unit 3: Ionic Bonding, Naming & Metallic Bonding

I. Properties of Ionic Compounds A. high melting & boiling points (above 300°C) B. most are crystalline solids at room temperature C. tend to be soluble (dissolve) in water D. can conduct electricity in a molten state or in solution E. crystallize as sharply defined particles F. generally form between metals (cations) & non-metals (anions)

II. Ionic Bonds Why do atoms bond? To be more stable (like noble gases). A. due to transfer of valence electrons B. oppositely charged ions (cation, anion) are attracted to each other C. monatomic ions = single atoms with a + or – charge. Ex: Ca 2+

D. polyatomic ions = 2 or more bonded atoms carrying a net + or - charge (see ion chart) Ex: NH 4 1+ *oxyanions- polyatomic anions containing oxygen Ex: SO 4 2- *the subscripts of a polyatomic ion can never be altered!!

III. Writing Chemical Formulas A. Formula unit – simplest whole # ratio of ions that yields a net zero charge 1. write cation first, then anion Li 1+ S determine the number of each ion that is needed to cancel the charges 2 Li 1+ 1 S 2- = Li 2 S 3. use parenthesis () around polyatomic ions if more than one is needed to balance the charge. Al 3+ NO 3 1- = Al(NO 3 ) 3

IV. Naming Ionic Compounds A.Rules 1. Name the cation first *include Roman numerals for transition metals with more than 1 possible charge. 2. Name the anion last * monatomic ions end with –ide * names of polyatomic ions never change!!

Examples: Na 2 O = sodium oxide CuCl 2 = copper (II) chloride SnS 2 = tin (IV) sulfide

V. Metallic Bonding A. occurs between 2 or more metal atoms B. Weaker than ionic bonds because electrons are not truly transferred. C.electron sea model - Metal atoms are packed together in a crystal lattice. The valence electrons are free to move between the metal ions (delocalized). The metal ions are held together by their attraction to the sea of electrons.

D. This explains the properties of metals (good conductors of electricity, lustrous, malleable, etc.) gMDP47s