Atoms and Ions march 22,2010

Atoms and Ions

• Atoms are electrically neutral
• # of protons = #of electrons
• Ions have different # of protons and electrons
• Ions can be either positive (lost e-) or negative (gained e-)
• Cations = positive ion
• Anions = negative ion

Examples

• Determine how many electrons each of the ions have. What type of ion are they (cation/Anion)

Ca2+ -> lost 2e-, 18 electrons, cation

F- -> gained 1 e-, 8 electrons, anion

H+ -> lost 1e-, 0 electrons, cation

H- -> gained 1 e-, 2 electrons, anion

Examples

76 As 3- -> 33 p+, 43 n, 36 electrons (gained 3)

201 Au+ -> 79p+, 122n, 78 electrons (lost 1)

Bohr diagrams for Ions

Bohr diagrams could also be written as:

8e-
2e- 2e-
10 4
9 F 3 Li

Chemical Bonds

• A bond is an electrostatic attraction btwn particles
• Bonds occur as elements try to achieve Noble gas electron configuration
• Noble gases (usually) do not form compunds or bonds
• 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
• Dots represent electrons
• Only Vanlence level electrons are shown
• Wtrite the atomic symbol for the atom
• -this rep. the nucleus and filled inner electron leves
• one dot is used to rep outer energy level electrons
• one e- is placed in each orbital before any pairing occurs
• - beginning with the 5th e-, pairing can occur up to a maximum of 8e-

Example

Carbon, Hydrogen, Nitrogen

Ionic Bonds (have brackets (covalent dont have brackets)

• electrons are transferred from metal to nonmental. no dots are shown on metal
• charged species is written in brackets