ion: a charged atom that has gained or lost an electron  atoms that lose electrons become ___ ions (called cations)  atoms that gain electrons become ___ ions (called anions) recall:  atoms ‘like’ to have ___ valence e - s to become stable  called the ‘octet rule’ Trends:  metals tend to ________ electrons and form ___ ions  nonmetals tend to ________ electrons and form ___ions lose + gain -

Na 11p 12n Sodium atom loses 1e - 11p + = e - = -11 Total = 0 i.e. No charge 11p + = e - = -10 Total = +1 i.e. +1 charge i.e. An atom that loses electrons becomes a POSITIVE ion Now its electron configuration looks like Neon, an inert gas  very stable! Notice that the nucleus does not change – still 11 protons, and therefore still a sodium atom!

Cl 17p 18n Chlorine atom gains 1e - 17p + = e - = -17 Total = 0 i.e. No charge 17p + = e - = -18 Total = -1 i.e. -1 charge i.e. An atom that gains electrons becomes a NEGATIVE ion. Now its electron configuration looks like Argon, an inert gas  very stable! Notice that the nucleus does not change – still 17 protons, and therefore still a CHLORINE atom!

H 1p 0n He 2p 2n Li 3p 4n N 7p 7n O 8p 8n F 9p 10n Ne 10p 10n Na 11p 12n Si 14p 14n P 15p 16n Cl 17p 18n S 16p 16n Ar 18p 22n K 19p 20n Be 4p 5n B 5p 6n Al 13p 14n Ca 20p 20n C 6p 6n Mg 12p 12n Li 3p 4n +1 O 8p 8n -2 Be 4p 5n +2 N 7p 7n -3 B 5p 6n +3 F 9p 10n Na 11p 12n +1 Al 13p 14n +3 P 15p 16n -3 Mg 12p 12n +2 Ca 20p 20n +2-2 S 16p 16n K 19p 20n +1 Cl 17p 18n (They either gain or lose electrons.) Noble gases don’t gain or lose electrons. (because their outer shells are “full”) These ones do something different... (more on that later...)

Group # # valence electrons ionic charge Example (really 13) 4 (really 14) 5 (really 15) 6 (really 16) 7 (really 17) 8 (really 18) 1+1Li 2 +2Be 3+3 Al 4 most won’t form ions, most like to share electrons 5 -3N 6-2O 7 F 8noneNe

 composed of a metal & a nonmetal  metal transfers its valence electrons to the nonmetal recall: opposite charges attract result: positive metallic ion & negative nonmetallic ion attract to form an ionic compound

Examples using Lewis Structures (shorthand using element symbol & dots for valence electrons) 1. sodium + chlorine sodium chloride (salt) Na Cl Na + Cl - NaCl

Examples using Lewis Structures (shorthand using element symbol & dots for valence electrons) 2. calcium + iodine calcium iodide Ca I 2+ I - CaI 2 I I -

Examples using Lewis Structures (shorthand using element symbol & dots for valence electrons) 3. aluminum + oxygen aluminum oxide Al O 3+ O 2- Al 2 O 3 O O 2- O O Al 3+

Examples using Lewis Structures (shorthand using element symbol & dots for valence electrons) 4. magnesium + sulfur magnesium sulfide Mg S 2+ S 2- MgS

 Page 142 # 1, 3ad (don’t name them, instead use Lewis structures to show the formation of each)  Page 146 # 5, 6  Page 151 # 3 (do Lewis not Bohr)  Page 174 # 2, 5