ions and ionic bonds. review octet rule atoms typically gain or lose valence e - so they will have...
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Ions and Ionic Bonds
Review Octet Rule
Atoms typically gain or lose valence e- so they will have the same e- configuration as a noble gas.
Most noble gases have 8 valence electrons. Helium has only 2 valence electrons.
The Octet Rule
Na Ne
8 valence electrons
1 valence electron
8 valence electrons
The Octet Rule
8 valence electrons
Cl
7 valence electrons
Ar
8 valence electrons
The Octet Rule
Li He
2 valence electrons
1 valence electron
2 valence electrons
•Ionic bonds are a type of chemical bond based on electrostatic forces between two oppositely-charged ions.
Ionic Bonds
•It is basically the transfer of one electron from one atom to another
•An ion is an atom or group of atoms that have a charge. Atoms normally have a neutral charge because most often they have the same number of electrons and protons. They become ions by the loss or addition of one or more electrons. This process is called ionization.
Ionic Bonds
•An ion that has more electrons than protons is called an anion, and an ion that has fewer electrons than protons is called a cation.
Ionic Bonds
•The name ion was given by a man named Michael Faraday, which comes from a Greek word meaning “to go” or “a goer”.
•The word anion comes from the Greek word meaning (a thing) “going up” and cation means (a thing) “going down”.
Ionic Bonds
Ionic Compounds Ionic compound (salt) – compound made of
cations and anions. cations are formed from metals anions are formed from non-metals
Ionic bond – the force that holds an ionic substance together.
Ionic Bonding
Na Cl
Na Cl+ -
Ionic bonds Occurs when:
1. a metal atom loses an electron and becomes a positive ion
2. a non-metal atom gains the electron and becomes a negative ion
3. the positive and negative attract each other and form a bond
Ionic Bonding
+
-- +
-- +
-- +
-
+
-
+
- +
-
+
- +
-
+
- +
-
+
-
+
- +
-
+
- +
-
+
- +
-+ + +
+ - + - + - +IMPORTANT: Although the ions in a salt are charged, the compound as a whole is not.
How do ionic bonds form Use the criss-cross method
Step 1- Identify the metal and non-metal Step 2- Write the symbols Step 3- write the charges Step 4- cross over the charges Step 5- remove the charge (+ -) Step 6- simplify the numbers and get rid of 1’s
NOTE: THE OVERALL CHARGE ON IONIC FORMULAS SHOULD ALWAYS EQUAL ZERO!!!!!!
Ionic Formulas Chemical formula – indicates the number and
type of atoms in a substance. H2O
2 hydrogen atoms + 1 oxygen atom NaNO3
1 sodium ion + 1 nitrogen atom + 3 oxygen atoms Formula unit – lowest whole-number ratio of ions
in a compound. The formula unit for table salt is NaCl. 1 unit of Na+ ions per 1 unit of Cl- ions. Formula does not show the charges of the ions.
Ionic Formulas What salt forms when aluminum combines with
chlorine? Aluminum has 3 valence electrons.
Loses 3 e- to reach octet. Forms Al+3 ion.
Chlorine has 7 valence electrions. Gains 1 e- to reach octet. Forms Cl-1 ion.
If the compound is neutral, it will take 1 Al+3 ion for every 3 Cl-1 ions.
The formula is AlCl3.
Aluminum + Chlorine
Al ClCl
Cl
Ionic Bonds – Writing FormulasIonic Bonds – Writing Formulas CRISS-CROSS METHOD
Oxidation numbers (excluding charge) of each ion trade places to become the subscripts in the formula – must be reduced to lowest whole number ratio; 1’s are not written
Ca & S
Ca2S2
Al & Cl
AlCl3
3+ 1- 2+ 2-
CaS
Writing Ionic Formulas Criss-Cross Method of writing ionic
formulas: Criss-cross charges to become subscripts Drop the charges when crossing over.
Example: What salt is formed from sodium and sulfur? Na forms +1 ions. S forms -2 ions. Na+1 + S-2 Na2S
Writing Ionic Formulas sodium + chlorine calcium + bromine lithium + oxygen aluminum + oxygen magnesium + nitrogen
Na+1 + Cl-1 Ca+2 + Br -1 Li+1 + O-2 Al+3 + O-2 Mg+2 + N-3
NaCl
CaBr2
Li2O
Al2O3
Mg3N2
Writing Ionic Formulas If the subscripts can be reduced, do so.
Example: calcium + oxygen Ions: Ca+2 + O-2
Wrong: Ca2O2
Right: CaO Example: lead + oxygen
Ions: Pb+4 + O-2
Wrong: Pb2O4
Right: PbO2
Ionic Bonds – Writing FormulasIonic Bonds – Writing Formulas
Sodium and chlorine bond in a 1:1 ratio to form NaCl
Calcium and chlorine bond in a 1:2 ratio for form CaCl2
What determines each ratio & formula? ________________
oxidation numbers
Ionic Bonds – Writing FormulasIonic Bonds – Writing Formulas
Ions Oxidation Numbers Ratio Formula
Magnesium & Oxygen Mg2+ & O2- 1:1 MgO
Lithium &
Sulfur
Aluminum & Oxygen
Sodium & Phosphorus
Barium &
Fluorine
Try to predict the ratio and resulting formula for each of the following ions based on their oxidation numbers:
Li+ & S2- 2:1 Li2S
Al3+ & O2- 2:3 Al2O3
Na+ & P3- 3:1 Na3P
Ba2+ & F- 1:2 BaF2
We will learn how to write nomenclature for: Ternary Salts
3 or more elements Includes a polyatomic ion
Salts with Multiple Oxidation Numbers Can be binary or ternary Includes a transition metal
Polyatomic Ions Polyatomic Ions – ions made of more than one
atom. Examples:
NO3-1
1 nitrogen atom and 3 oxygen atoms that collectively have a -1 charge.
SO4-2
1 sulfur atom and 4 oxygen atoms that collectively have a -2 charge.
PO4-3
1 phosphorus atom and 4 oxygen atoms that collectively have a -3 charge.
NH4+1
1 nitrogen atom and 4 hydrogen atoms that collectively have a +1 charge.
Polyatomic Ions in Salts Treat them like single-atom ions.
But do not change their formula!
If you need more than one of a particular polyatomic ion, use parentheses. Example:
Na+1 + NO3-1 NaNO3
Mg+2 + NO3-1 Mg(NO3)2
Al+3 + NO3-1 Al(NO3)3
Polyatomic Ions in Salts K+1 + OH-1 Ca+2 + OH-1 Ga+3 + OH-1 NH4
+1 + Cl-1 NH4
+1 + S-2 NH4
+1 + P-3 NH4
+1 + SO4-2
KOH
Ca(OH)2
Ga(OH)3
NH4Cl
(NH4)2S
(NH4)3P
(NH4)2SO4
Polyatomic IonsPolyatomic IonsName Formula
acetate C2H3O2- or
CH3COO-
ammonium NH4+
carbonate CO32-
chlorate ClO3-
chlorite ClO2-
chromate CrO42-
cyanide CN-
dichromate Cr2O72-
hydrogen carbonate HCO3-
hydroxide OH-
hypochlorite ClO-
nitrate NO3-
nitrite NO2-
perchlorate ClO4-
permanganate MnO4-
phosphate PO43-
sulfate SO42-
sulfite SO32-
Some ions contain more than one element - called a polyatomic ion
The group as a whole has an overall charge
Examples: Lithium and sulfate would
bond together to make Li2SO4
Ammonium and sulfur would bond together to make (NH4)2S
Ternary Salt NamingTernary Salt Naming Contains 3 or more elements: cation & anion – most polyatomic
ions are anions, only cation is ammonium (NH4+)
Naming: Name the cation (no changes) Name the anion (no changes)
Example: Na2SO4 = sodium sulfate Exception: When ammonium is paired with an element anion
NH4Cl = ammonium chloride
Ternary Salt FormulasTernary Salt Formulas You must use parentheses if you have more
than one polyatomic ion. Be sure to criss-cross the oxidation numbers and write it OUTSIDE of the parentheses.
K & PO4
K3PO4
Al & SO3
Al2(SO3)3
3+ 2- + 3-
Ternary Salt Formulas & NamingTernary Salt Formulas & Naming
IonsOxidation Numbers
Ratio Formula Name
Potassium & Hydroxide K+ & OH- 1:1 KOH
potassium hydroxide
Calcium & Carbonate
Barium &
Nitrate
Sodium & Phosphate
Ammonium & Sulfur
Try to predict the formulas and names for each ternary salt:
Ca2+ & CO32- 1:1 CaCO3
calcium carbonate
Ba2+ & NO3- 2:1 Ba(NO3)2
barium nitrate
Na3PO4Na+ & PO43- 1:3 sodium
phosphate
NH4+ & S2- 1:2 (NH4)2S
ammonium sulfide
Salts with Multiple Oxidation #s NamingSalts with Multiple Oxidation #s Naming
Transition elements can form more than one type of positive ion. For example, copper can form both Cu+ and Cu2+ ions,
and iron can form both Fe2+ and Fe3+ ions. Zinc and silver are two exceptions – they only have one
oxidation number The zinc ion is Zn2+ and the silver ion is Ag+.
Salts with Multiple Oxidation #s NamingSalts with Multiple Oxidation #s Naming
Transition elements can form more than one type of positive ion.
Naming: Name the cation Put the roman numeral representing the oxidation # of the
metal in parentheses (do not indicate the charge) Name the anion, changing the ending to “ide” (binary) or
naming the polyatomic ion (ternary) Example:
FeCl2 = iron (II) chloride FeCl3 = iron (III) chloride
Salts with Multiple Oxidation Salts with Multiple Oxidation Numbers PracticeNumbers Practice
IonsOxidation Numbers
Ratio Formula Name
Copper & Nitrate
Cu+ & NO3- 1:1 CuNO3
copper (I) nitrate
Lead &
Oxygen
Cobalt &
Hydroxide
Nickel & Phosphate
Chromium & Sulfur
Pb4+ & O2- 2:1 PbO2lead (IV)
oxide
Co3+ & OH- 3:1 Co(OH)3cobalt (III) hydroxide
Ni2+ & PO43- 2:3 Ni3(PO4)2
nickel (II) phosphate
Cr2+ & S2- 1:1 CrS chromium (II) sulfide