Atoms and Ions

• atoms are electrically neutral
• number of protons= number of electrons
• ions ahve different number of protons and electrons
• ions can be either positive of negative
• cation: positive ion
• anion: negative ion

Example: how many electrons do these electrons have? what type of ions are they?


S^2-: anion, sulphide ion I^1- : anion, iodide ion


chemical bonds

• a bond is an electrostatic attraction between particles
• bonds occur as elements try to acheieve noble gas electron configuration
• noble gases (usually) do not form compounds
• in noble gases the outermost energy level have stable octets
• metals lose electrons (oxidize)
• non metals gain electrons (reduced)

Lewis Dot Structure

• atoms can be represented by dot diagrams where dots represent electrons and only the valence level electrons are shown
• write the atomic symbol for the atom. this represents the nucleus and filled inner electron levels
• one dot is used to represent outer energy level electrons. one e- placed in each orbital before and pairing occurs. beginning with the 5th e-, pairing can occur up to a maximum of 8 e-

we practiced drawing lewis dot diagrams

Ionic Bonds

• electrons are transferred from metal to nonmetal. no dots are shown on the metal
• "charged" specie is written in brackets

so thats pretty much all we did today! lots of notes and lots of drawing :P