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Welcome Back!!• This semester…• January- Bonding and Naming Ionic
and Covalent Compounds• Jan/February- Finish Bonding &
Reactions• After Feb. break- Stoichiometry• March/April- Thermo, Gases• April- Acids and Bases• May- Solutions & Final Exam Review
Chemical Bondingand
Nomenclature
Valence electrons• The electrons in the highest energy level of
an atom.• s and p electrons*• *d electrons are never valence electrons
• Total # of s and p electrons
in a “FULL” energy level = 8
(THE OCTET RULE)
Lewis Structures
• We include only valence electrons
Water
How many valence electrons?
LEWIS DOT STRUCTURES FOR THE FIRST 20 ELEMENTS
Bonding• Chemical bond:
• A force that holds groups of two or more atoms together and makes them function as a unit
• Fundamental types of bonds• Ionic• Covalent• Metallic
• Bonds form in order to achieve a full outer shell (8) of electrons to:• Decrease potential energy (PE)• Increase stability
Ionic bonding• Described as a TRANSFER OF
ELECTRONS• Takes place between metals and
nonmetals. Nonmetals “want” electrons and metals “want” to give electrons away.
• Atoms become ions by gaining or losing electrons
• Oppositely charged ions are attracted to one another: this attraction is an “ionic bond.”
• Results in an ionic COMPOUND
Metals and Nonmetals Create Ionic Bonds
Ions
• Cation• Positively charged• Atom has LOST one or more
electrons• Metals tend to become cations
• Anion• Negatively charged• atom has GAINED one or more
electrons• Nonmetals tend to become anions
Types of ions
• Monatomic ion• Cation or anion that consists of a
single type of element• Ex: Li+, Br-
• Polyatomic ion• 2 or more elements that are
combined, but act as a single ion (or particle)
• Ex: CO32- or NH4
+
Formula units• Ionic compounds are represented by
formula units: similar to “molecule” except ionic compounds exist as a 3D network of multiple formula units because of the electrostatic attraction of opposite charges.
• The lowest whole number ratio of ions in an ionic compound is a formula unit.
NaClCaO
MgCl2
Al2O3
Types of ionic compounds
COMPOUND
TernaryCompound
BinaryCompound
2 elements
more than 2Elements
Means there is a Polyatomic ion present
NaNO3NaCl
Rule of Zero Charge• The charges on the metal cations (+)
and nonmetal anions (-) add up to zero.• Ex: Na+ and Cl- add up to an overall
charge of zero, so the formula unit is NaCl
• Ex: Ca2+ and O2- add up to an overall charge of zero, so the formula unit is CaO
Writing Binary Ionic Compounds
• RULES:
****Cation always listed first****
1. Drop Charges
2. Criss Cross Apple Sauce
3. Reduce (simplify) subscripts if needed
• Na+ and Cl- NaCl
What if the charges are opposite, but not equal???
• Criss-cross the charge values to subscripts• Ex: Al3+ + O2- is represented as Al2O3
• Ex: Mg2+ + Cl- is represented as MgCl2
• But why?• Because the overall charge
must be zero• All atoms “want” a full valence
Naming Binary ionic compounds
1. List name of cation• If metal cation is not a transition
element, give it the same name as the element and move on to anion.
• If cation can have more than one charge (i.e. most transition metals), use roman numerals in parentheses to specify charge.
For Example:Iron has 2 common oxidation states (charges): Fe2+ and Fe3+
• Fe2+ would be iron (II)• Fe3+ Would be iron (III)
CaO
Fe2O3
Naming Binary ionic compounds
• Name the cation first• Name the anion last; for binary
compounds, it always ends in –ide.
• Examples:
CaO would be calcium oxide
Fe2O3 is iron (III) oxide
NaCl is sodium chloride
AgCl is silver chloride
Common anion endings
• P- phosphide F-fluoride
• O-oxide Br- bromide
• S- sulfide I- iodide
• Cl-chloride C- carbide
• N-nitride
Some common polyatomic ions
Polyatomic Ions- QUIZ Friday!!• Add these to your list:
• bromate, BrO3-
• iodate, IO3-
• thiocyanate, SCN -
• hydrogen carbonate, HCO3- (also
called bicarbonate)• hydride, H- is NOT part of the list to
memorize
• THERE ARE 26 to memorize
Naming polyatomic anions: these just have to be memorized!
• With anions that end in oxygen, if you know one , you can figure out the other!
# of oxygens naming convention
1 less (PO33-) ends in –ite(phosphite)
1 more (PO43-) ends in –ate(phosphate)
Notice that within one group of polyatomic ions, the charges are the same!
Writing formulas for ternary compounds
• If more than 1 of a polyatomic ion is present, write parentheses around any polyatomic ion and add subscripts to the outside of the parentheses.
• Never change the subscript of a polyatomic ion (it will change the composition of the ion):• Ca(OH)2, Ca3(PO4)2
• Include the subscript inside the parentheses
Naming ternary ionic compounds
• For a monatomic cation and polyatomic anion, write both names together; do not change them in any way
• Ex: Na2SO4 is sodium sulfate
• For a polyatomic cation with a monatomic anion, write the polyatomic ion’s name first, then the monatomic root with the –ide ending
• Ex: NH4Cl is ammonium chloride
Metallic Bonding
• Metals form lattices but do not lose, gain, or share e-
• Outer e- shells overlap = electron sea model
• e- are free to move = delocalized e- making a metallic cation
• Metallic bond: attraction of a metallic cation for delocalized electron
• Properties of metals: melting point varies greatly, malleable, ductile, good conductors
Sea of electrons
Ionic Metallic
• Electron sea model – delocalized electrons attracted to metal cations
• Malleable, ductile, lustrous, colorful
• Conducts electricity
• Overall highest MP of 3 types
All bonding involves valence
electrons
Both involve metals
• Oppositely charged ions attracted to each other (cations and anions)
• Metals with non-metals
• Brittle, dull solids
• Only conducts electricity as electrolytes
• Generally, medium MP of 3 types
Covalent bonding
Covalent bonds
• Occur between atoms that are “sharing” electrons• Form covalent compounds
QUIZ: 1-5, NAME THE COMPOUND…6-10, WRITE THE FORMULA1) SrO
2) NaClO3
3) AlF3
4) NH4OH
5) Fe3(PO3)2
6) barium nitrite
7) potassium chloride
8) manganese (II) iodide
9) copper (II) acetate
10) sodium carbonate