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Valence Electrons, Ions, and Lewis Dot Diagrams. Unit 4. Keeping Track of Electrons. The electrons responsible for the chemical properties of atoms are those in the outer energy level. Valence electrons Valence electrons - The s and p electrons in the outer energy level. - PowerPoint PPT Presentation
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Valence Electrons, Ions, and Lewis Dot Diagrams
Unit 4
Keeping Track of Electrons
The electrons responsible for the chemical properties of atoms are those in the outer energy level.Valence electrons
Valence electrons - The s and p electrons in the outer energy level.
Core electrons -those in the energy levels below.
Keeping Track of Electrons
Atoms in the same columnHave the same outer electron configuration.Have the same valence electrons.
Easily found by looking up the group number on the periodic table.
Group 2A - Be, Mg, Ca, etc.- 2 valence electrons
Lewis Dot diagrams
A way of keeping track of valence electrons.
How to write themWrite the symbol.Put one dot for each valence
electronDon’t pair up until they have to
Xe
The Lewis Dot diagram for Nitrogen
Nitrogen has 5 valence electrons.
First we write the symbol.
NThen add 1 electron at a time to each side.Until they are forced to pair up.
Write the Lewis dot diagram for
NaMgCOFNeHe
Electron Configurations for Cations
Metals lose electrons to attain noble gas configuration.
They make positive ions.If we look at electron configuration it
makes sense.Na 1s22s22p63s1 - 1 valence electronNa+ 1s22s22p6 -noble gas configuration
Electron Dots For Cations
Metals will have few valence electrons
Ca
Electron Dots For Cations
Metals will have few valence electronsThese will come off
Ca
Electron Dots For Cations
Metals will have few valence electronsThese will come offForming positive ions
Ca+2
Electron Configurations for Anions
Nonmetals gain electrons to attain noble gas configuration.
They make negative ions.If we look at electron configuration it makes
sense.S 1s22s22p63s23p4 - 6 valence electronsS-2 1s22s22p63s23p6 -noble gas
configuration.
Electron Dots For Anions
Nonmetals will have many valence .electrons.
They will gain electrons to fill outer shell.
P P-3
Stable Electron Configurations
All atoms react to achieve noble gas configuration.
Noble gases have 2 s and 6 p electrons.8 valence electrons .Also called the octet rule.
Ar
+2
+1
+3 -3 -2 -1
Unit 4: Chapter 8
Ionic Bonding
+2
+1
+3 -3 -2 -1
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
Ionic Bonding
Anions and cations are held together by opposite charges.
Ionic compounds are called salts.Simplest ratio is called the formula unit.The bond is formed through the transfer of
electrons.Electrons are transferred to achieve noble
gas configuration.
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.
Ionic solids are brittle
+ - + -+- +-
+ - + -+- +-
Ionic solids are brittle
+ - + -
+- +-+ - + -
+- +-
Strong Repulsion breaks crystal apart.
Ionic Bonding
Na Cl
Ionic Bonding
Na+ Cl-
Ionic Bonding
All the electrons must be accounted for!
Ca P
Ionic Bonding
Ca P
Ionic Bonding
Ca+2 P
Ionic Bonding
Ca+2 P
Ca
Ionic Bonding
Ca+2 P-3
Ca
Ionic Bonding
Ca+2 P-3
Ca P
Ionic Bonding
Ca+2 P-3
Ca+2 P
Ionic Bonding
Ca+2 P-3
Ca+2 P
Ca
Ionic Bonding
Ca+2 P-3
Ca+2 P
Ca
Ionic Bonding
Ca+2 P-3
Ca+2P
-3
Ca+2
Ionic Bonding
Ca3P2
Formula Unit
Naming ions
We will use the systematic way.Cation- if the charge is always the same
(Group A) just write the name of the metal.Examples
Sodium ion = Na+
Barium ion = Ba2+
Silver ion = Ag+
Zinc ion = Zn2+
Naming Anions
Anions always have the same charge.Change the element ending to – ideExamples
Fluorine as an ion= F-1 fluorideChlorine as an ion= Cl- chlorideOxygen as an ion= O2- oxide
Name these
Cl-1 N-3 I-1 S-2
Chloride ionNitride ionIodide ionSulfide ion
Write these
Oxide ionFluoride ionPhosphide ionStrontium ion
O2-
F-
P3-
Sr2+
Naming Binary Ionic Compounds
Binary Compounds - 2 elements.Ionic - a cation and an anion.To write the names just name the two
ions.Easy with Representative elements
(Group A)NaCl = Na+ Cl- = sodium chloride
MgBr2 = Mg+2 Br- = magnesium bromide
Writing Formulas
The charges have to add up to zero.Get charges on pieces.Charges for Cations come from the
periodic table.If it is a transition metal, the charge is the
roman numeralAnions from the periodic table.Criss- Cross the charges to determine
subscripts
The Criss-Cross Rule
Write the formula for calcium chloride.Calcium is Ca+2 Chloride is Cl-1 Criss Cross the charges to determine the
subscripts
Ca+2 Cl-1( only the numbers, not the signs)
ANSWER: CaCl2
Naming ions with Transition Metals
Transition metals can have more than one type of charge.
Indicate the charge with roman numerals in parenthesis.
ExamplesNi+2 = nickel (II) ionNi+ = nickel (I) ion
Naming Binary Ionic Compounds
Write the formulas for each the following
1. Chromium (III) nitride
2. Scandium (II) phosphide
3. Lead (II) oxide
4. Lead (IV) oxide
•CrN
•Sc3P2
•PbO
•PbO2
Naming Binary Ionic Compounds with Transition Metals
The problem comes with the transition metals.
Need to figure out their charges.The compound must be neutral.
same number of + and – charges.
Use the anion to determine the charge on the positive ion.
Naming Binary Ionic Compounds
Write the name of CuONeed the charge of CuO is -2copper must be +2
ANSWER: Copper (II) oxide
Name CoCl3
Cl is -1there are three of them = -3
Co must be +3 ANSWER: Cobalt (III) chloride
Naming Binary Ionic Compounds
Write the name of Cu2S.Since S is -2, the Cu2 must be +2, so each one
is +1.ANSWER: copper (I) sulfide
Fe2O3 Each O is -2 3 x -2 = -62 Fe must = +6, so each is +3.
ANSWER: iron (III) oxide
Write the formulas for these
Lithium sulfide
tin (II) oxide
tin (IV) oxide
Magnesium fluoride
Iron (III) phosphide
Iron (III) sulfide
1. Li2S
2. SnO
3. SnO2
4. MgF2
5. FeP
6. Fe2P3
Polyatomic ions
Groups of atoms that stay together and have a charge.
You must memorize these by the midterm
Nitrate NO3-1
Hydroxide OH-1
Sulfate SO4-2
Phosphate PO4-3
Ammonium NH4+1
Write the formulas for these
Ammonium chlorideammonium sulfidebarium nitrateCopper (II) sulfategallium nitrate
Ternary Ionic Compounds
NaNO3
CaSO4
CuSO3
(NH4)2O
Ternary Ionic Compounds
LiCN
Fe(OH)3
(NH4)2CO3
NiPO4
Things to look for
If cations have (), the number is their charge.If not it only has 1 charge, look on the periodic
table
If anions end in -ide they are probably off the periodic table (Monoatomic)
If anion ends in -ate or -ite it is polyatomic
Metallic Compounds
Metallic Bonds
How atoms are held together in the solid.Metals hold onto there valence electrons
very weakly.Think of them as positive ions floating in a
sea of electrons.
Sea of Electrons
+ + + ++ + + +
+ + + +
Electrons are free to move through the solid.Electrons are said to be “delocalized”
Metals conduct electricity.
Properties of Metallic Compounds
Metal ions bonded togetherCan be atoms of different metals
Hammered into shape (bend).Ductile - drawn into wires.Melting and boiling points vary (based on
metal)Good conductors of electricity as a solid
Malleable
+ + + ++ + + +
+ + + +
Malleable
+ + + +
+ + + ++ + + +
Electrons allow atoms to slide by.
