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Chemical Bonds. An electrical attraction between two oppositely charged atoms or groups of atoms. Happens when an atom of a nonmetal takes one or more electrons from an atom of a metal so both atoms end up with eight valence electrons. IONIC BONDING. The Octet Rule. - PowerPoint PPT Presentation
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IONIC BONDING
Happens when an atom of a nonmetaltakes one or more electrons
from an atom of a metalso both atoms end up with
eight valence electrons
An electrical attraction between two oppositely charged atoms or groups of atoms.
The Octet Rule
• The octet rule says that atoms can become stable by having eight electrons in their outer energy level, as shown in the noble gas, Neon, (or two electrons in the case of some of the smallest atoms).
Electron Dots For Cations Metals will have few valence electrons These will come off
Ca
Electron Dots For Cations Metals will have few valence electrons These will come off Forming positive ions
Ca2+
Electron Dots For Anions
Nonmetals will have many valence electrons.
They will gain electrons to fill outer shell.
P P3-
IONIC COMPOUNDS
metal with nonmetal + ion - ion Ca+ion anion
Predicting Oxidation Number or Charge from Periodic Table
Forming Cations
metals lose e- form cations oxidation #
group 1A lose 1 +1 charge 1 + group 2A lose 2 +2 charge 2 + group 3A lose 3 +3 charge 3 + group 4A lose 4 +4 charge 4 +
Forming Anions
Non-metals gain e- form anions oxidation #
group 7A gain 1 -1 charge 1 -
group 6A gain 2 -2 charge 2 - group 5A gain 3 -3 charge 3 -
1
7
4
5
6
2
3
+1
+2
+3 +4
-3 -2 -1
0
+2
+2
+3
+1
Oxidation Numbers
Neutral atoms come near each other.
Electron(s) are transferred from the Metal atom to the Non-metal atom.
They stick together because of electrostatic forces, like magnets.
IONIC BONDING
Steps for writing ionic bond formulas 1. Determine the oxidation numbers
for the two elements or ions.
Ca = +2, Cl = -1
Steps for writing ionic bond formulas 2. Write the chemical symbols in the
correct order, with the metal ion first and write the oxidation numbers as superscripts. Ca 2+ Cl -1
Ca 2+ Cl 1-
3. Crisscross the numbers only—not the charge signs—writing the oxidation number of one element as a subscript for the other. Don’t write number 1 either.
Ca 1 Cl 2
Steps for writing ionic bond formulas
Ca Cl2
4. Determine whether the formula is in its simplest form. Reduce the subscripts to the simplest from by dividing by a common denominator.
CaCa+2+2 OO-2-2
CaCa22 OO22 = Ca= Ca22OO22
CaOCaO
Steps for writing ionic bond formulas
5. Check the formula by calculating the total positive and negative charges and confirming that the total charge on the compound is zero.
CaCl 2
Steps for writing ionic bond formulas
Oxidation Number
Subscript
Calcium (+2) x (1) = +2
Chlorine (-) x (2) = -2
Practice these!
magnesium and oxygen aluminum and bromine sodium and sulfur potassium and nitrogen
MgO
AlBr3
Na2S
K3N
More Practice!
potassium bromidecalcium oxideSilver fluoride
KBrCaOAgF
Polyatomic ions
Groups of atoms that stick together as a unit, and have a charge
PO43- phosphate
CO32- carbonate
C2H3O41- acetate
Names often end in –ate or –ite
6. POLYATOMIC IONS ACT JUST LIKE ANY OTHER NEGATIVE ION WHEN BONDINGTreat polyatomic ion as single unit—don’t change it in any way!
Steps for writing ionic bond formulas
Steps for writing ionic bond formulas
polyatomic ions are enclosed in parenthesis if taken more than once in the formula. A subscript outside the parenthesis multiplies everything inside.
Steps for writing ionic bond formulas
Steps for writing ionic bond formulas
potassium hydroxide
zinc (II) carbonate
barium chlorate
aluminum phosphate
Practice
KOHKOH
ZnCOZnCO33
Ba(ClOBa(ClO33))22
AlPOAlPO44
calcium acetate
sodium nitrate
aluminum hydroxide
ammonium phosphate
More Practice
Ca(CCa(C22HH33OO22)) 2 2
NaNONaNO33
Al(OH)Al(OH) 3 3
(NH(NH44))3 3 POPO44
Naming Ionic Compounds1. name cation - then anion
2. if anion (nonmetal) is a single element ….. then name ends in “-ide”
3. If metal have more than one possible charge (include roman numeral in parenthesis to give charge)*
*All metals except: Ag+1, Zn+2, Cd+2, Al+3
Naming Ionic Compounds
Na2O
Mg(OH)2
Al(NO3)3
NH4Cl
Practice (no transitional metals)
Sodium oxideSodium oxide
Manganese (II) oxideManganese (II) oxide
Aluminum nitrateAluminum nitrate
Ammonium chlorideAmmonium chloride
Sn(ClO3)4
Cu2CO3
Fe2O3
NiSO4
Practice with transitional metals
Tin(IV) chlorateTin(IV) chlorate
Copper (I) carbonateCopper (I) carbonate
Iron (III) oxideIron (III) oxide
Nickel (II) sulfateNickel (II) sulfate
Hint: look at the subscript in the anion to predict the metal oxidation number.
Properties of Ionic Compounds Crystalline structure. A regular repeating arrangement of
ions in the solid. Ions are strongly bonded. Structure is rigid. High melting points- because of
strong forces between ions.
Crystalline structure
3 dimension
The repeating unit is called the unit cell
Crystalline structure
+
+
+ +
+
+
++
+
--
--
- --
--
The POSITIVE CATIONS
stick to the NEGATIVE ANIONS,
like a magnet.
Ionic solids are brittle
+ - + -+- +-
+ - + -+- +-
Ionic solids are brittle
+ - +-
+- +-+ - + -+- +-
Strong Repulsion breaks crystal apart.
Cubic
Body-Centered Cubic
Face-Centered Cubic
Do they Conduct? Conducting electricity is allowing
charges to move. In a solid, the ions are locked in place. Ionic solids are insulators. When melted, the ions can move
around. Melted ionic compounds conduct. First get them to 800ºC. Dissolved in water they conduct.