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Chapter 7
“Ionic and Metallic Bonding”
7.1 - Ions
Valence Electrons are…? Valence electrons –
The s and p electrons in the outer energy level– the highest occupied energy level
Core electrons – electrons in the energy levels below.
Keeping Track of Electrons Atoms in the same column...
1) Have the same outer electron configuration.
2) Have the same valence electrons.1) Electron configuration of Group 1A?
2) Number of valence electrons in Group 1A?– 1
The number of valence electrons are easily determined. It is the group number for a representative element
Group 2A: Be, Mg, Ca, etc.– have 2 valence electrons
Electron Dot diagrams are… A way of showing
valence electrons. How to write them? Write the symbol –
represents the nucleus and inner (core) electrons
Put one dot for each valence electron (8 maximum)
They don’t pair up until they have to (Hund’s rule)
X
The Electron Dot diagram for Nitrogen
Nitrogen has 5 valence electrons to show.
First we write the symbol. NThen add 1 electron at a time to each side.
Now they are forced to pair up.We have now written the electron dot diagram for Nitrogen.
Practice with e- dot structure Li
Be
B
C
N
O
F
Ne
The Octet Rule The Octet Rule:
in forming compounds, atoms tend to achieve a noble gas configuration; 8 in the outer level
Each noble gas (except He, which has 2) has 8 electrons in the outer level
Formation of Cations Metals lose electrons
to attain a noble gas configuration.–Where are metals located? Left
Make positive ions (cations)
Formation of Cations If we look at the electron configuration, it
makes sense to lose electrons: Na 1s22s22p63s1 1 valence electron Na1+ 1s22s22p6
This is a noble gas configuration with 8 electrons in the outer level.
Electron Dots For Cations Metals will have few valence
electrons (usually 3 or less); calcium has only 2 valence electrons
Ca
Electron Dots For Cations Metals will lose all
valence electrons
Ca
Electron Dots For Cations Metals will lose the valence electrons Form positive ions
Ca2+
NO DOTS are now shown for the cation.
This is the “calcium ion”.
Practice # of valence electron
Na = 1
Mg = 2
Al = 3
Cation formed
The transition metals get
funky…
Electron Dots For Cations Let’s do Scandium, #21 The electron configuration is:
1s22s22p63s23p64s23d1
Thus, it can lose 2e- (making it 2+), or lose 3e- (making 3+)
Sc = Sc2+
Scandium (II) ion Scandium (III) ion
Sc = Sc3+
Electron Dots For Cations Let’s do Silver, element #47 Predicted configuration is:
1s22s22p63s23p64s23d104p65s24d9
Actual configuration is: 1s22s22p63s23p64s23d104p65s14d10
Ag = Ag1+ (can’t lose any more, charges of 3+ or greater are uncommon)
Electron Dots For CationsSilver did the best job it
could, but it did not achieve a true Noble Gas configuration
Instead, it is called a “pseudo-noble gas configuration”
Electron Configurations: Anions Nonmetals gain
electrons to attain noble gas configuration.
They make negative ions (anions) S = 1s22s22p63s23p4 = 6 valence electrons S2- = 1s22s22p63s23p6 = noble gas
configuration. Halide ions - ions from
chlorine or other halogens that gain electrons
Electron Dots For Anions Nonmetals will have many
valence electrons (usually 5 or more) They will gain electrons to fill outer shell.
P 3-(This is called the “phosphide ion”, and shows dots)
Stable Electron Configurations All atoms react to try and achieve a noble
gas configuration. Noble gases have 2 s and 6 p electrons. 8 valence electrons = stable This is the octet rule
(8 in the outer level is particularly stable).
Ar
ReviewHow many valence electrons do the following
elements have?
Ga = 3 P = 5 Cl = 7 S = 6 Mg = 2
K = 1 Li = 1 He = 2 F = 7 Ne = 8
ReviewDraw the electron dot structure of the following
elements. Ga
P
S
Mg
K
He
F
Ne
ReviewWhat ions will the following elements form?
7.2 - Ionic Bonds and Ionic
Compounds
Ionic Bonding Anions and cations are held together by
opposite charges (+ and -) Ionic compounds are called salts. Formula unit –
Simplest ratio of elements in an ionic compound.
Practice with Formula Unit What is the formula unit for the following
compounds? Formula Unit
NaCl 1:1 2:1 1:1:3
Ionic Bonds Formed through the
transfer of electrons (lose and gain)
Electrons are transferred to achieve noble gas configuration.
Ionic Compounds1) Also called SALTS
2) Made from a CATION and ANION
• A metal and a nonmetal)
Ionic Bonding
Na Cl• The metal loses
its one electron from the outer level.• The nonmetal gains
one more to fill its outer level, and will accept the one electron that the metal is going to lose.
Ionic Bonding
Na+ Cl -
Note: Remember that NO DOTS are now shown for the cation!
Ionic Bonding
All electrons must be accounted for, and each atom will have a noble gas configuration (which is stable).
Ca P
Example- combine Ca and P:
Ionic Bonding
Ca P
Ionic Bonding
Ca2+ P
Ionic Bonding
Ca2+ P
Ca
Ionic Bonding
Ca2+ P 3-
Ca
Ionic Bonding
Ca2+ P 3-
Ca P
Ionic Bonding
Ca2+ P 3-
Ca2+ P
Ionic Bonding
Ca2+ P 3-
Ca2+ P
Ca
Ionic Bonding
Ca2+ P 3-
Ca2+ P
Ca
Ionic Bonding
Ca2+ P 3-
Ca2+P
3-
Ca2+
Ionic Bonding
= Ca3P2
• Chemical formula- shows the kinds and numbers of atoms in the smallest representative particle of the substance.
Balancing Ionic formulas Crisscross method The numerical value of the
charge of each ion is crossed over and becomes the subscript for the other ion.
PracticeWhat will the chemical formula look like?
Elements
Ca+2 F-
Al+3 O-2
Ca+2 O-2
Formula
Properties of Ionic Compounds1. Crystalline solids –
regular repeating arrangement of ions Strongly bonded together. Structure is rigid.
2. High melting points Coordination number-
number of ions of opposite charge surrounding it
- Page 198
Coordination Numbers:
Both the sodium and chlorine have 6
Both the cesium and chlorine have 8
Each titanium has 6, and each oxygen has 3
NaCl
CsCl
TiO2
Do they Conduct? Conducting electricity means
allowing charges to move. In a solid, the ions are locked in place. Ionic solids are insulators. When melted, the ions can move.3. Melted ionic compounds conduct.– NaCl: must get to about 800 ºC.– Dissolved in water,
they also conduct (free to move in aqueous solutions)
- Page 198
The ions are free to move when they are molten (or in aqueous solution), and thus they
are able to conduct the electric current.
ReviewWhat is the formula unit for the following
compounds?
KCl 1:1
1:2
HgS 1:1
2:3
1:1:4
2:1
PracticeWhat will the chemical formula look like?
Elements Na+ Cl- Mg+2F- Ca+2 N-3 Al+3 N-3 K+ S-2
Formula
7.3 – Bonding in
Metals
Metallic Bonds are… How do we get sheets of Aluminum (or any
metal)? Metals hold on to their valence electrons
very weakly. Think of them as positive ions (cations)
floating in a sea of electrons
Sea of Electrons
+ + + ++ + + +
+ + + +
Electrons are free to move through the solid.
Metals conduct electricity.
Metals are Malleable Hammered into shape (bend). Ductile - drawn into wires. Both malleability and ductility explained in
terms of the mobility of the valence electrons
- Page 201
1) Ductility 2) Malleability
Due to the mobility of the valence electrons, metals have:
and
Notice that the ionic crystal breaks due to ion repulsion!
Malleable
+ + + ++ + + +
+ + + +
Force
Malleable
+ + + +
+ + + ++ + + +
Mobile electrons allow atoms to slide by, sort of like ball bearings in oil.
Force
Ionic solids are brittle
+ - + -+- +-
+ - + -+- +-
Force
Ionic solids are brittle
+ - + -
+- +-+ - + -
+- +-
Strong Repulsion breaks a crystal apart, due to similar ions being next to each other.
Force
Crystalline structure of metal Metals are arranged in very compact
and orderly patterns.
Alloys Alloys - mixtures of 2 or
more elements, at least 1 is a metal Made by melting a
mixture of elements, then cooling Brass: an alloy of Cu and Zn Bronze: Cu and Sn
Why use alloys? Properties are often superior
to the pure element Sterling silver (92.5% Ag, 7.5% Cu) is
harder and more durable than pure Ag, but still soft enough to make jewelry and tableware
Steels are very important alloys–corrosion resistant, ductility, hardness,
toughness, cost
The
•END
Predicting Ionic ChargesGroup B elements: Many transition elements
have more than one possible oxidation state.Iron (II) = Fe2+
Iron (III) = Fe3+
Note the use of Roman numerals to show charges
Naming cations Two methods can clarify when
more than one charge is possible:
1) Stock system – uses roman numerals in parenthesis to indicate the numerical value
2) Classical method – uses root word with suffixes (-ous, -ic)• Does not give true value
Naming cations We will use the Stock system. Cation - if the charge is always the
same (like in the Group A metals) just write the name of the metal.
Transition metals can have more than one type of charge.– Indicate their charge as a roman
numeral in parenthesis after the name of the metal (Table 9.2, p.255)
Predicting Ionic Charges Some of the post-transition elements also have more than one possible oxidation state.Tin (II) = Sn2+ Lead (II) = Pb2+
Tin (IV) = Sn4+ Lead (IV) = Pb 4+
Predicting Ionic ChargesGroup B elements: Some transition elements have only one possible oxidation state, such as these three:
Zinc = Zn2+Silver = Ag1+ Cadmium = Cd2+
Exceptions:Some of the transition metals
have only one ionic charge:
–Do not need to use roman numerals for these:
–Silver is always 1+ (Ag1+)–Cadmium and Zinc are always
2+ (Cd2+ and Zn2+)
Practice by naming these: Na1+ Ca2+ Al3+ Fe3+ Fe2+ Pb2+ Li1+
Write symbols for these:
Potassium ionMagnesium ion Copper (II) ionChromium (VI) ionBarium ionMercury (II) ion
Naming AnionsAnions are always the
same chargeChange the monatomic
element ending to – ideF1- a Fluorine atom will
become a Fluoride ion.
Practice by naming these:Cl1- N3- Br1- O2-
Ga3+
Write symbols for these:
Sulfide ionIodide ionPhosphide ionStrontium ion
Polyatomic ions are… Groups of atoms that stay together and
have an overall charge, and one name. Usually end in –ate or -ite
Acetate: C2H3O21-
Nitrate: NO31-
Nitrite: NO21-
Permanganate: MnO41-
Hydroxide: OH1- and Cyanide: CN1-?
Sulfate: SO42-
Sulfite: SO32-
Carbonate: CO32-
Chromate: CrO42-
Dichromate: Cr2O72-
Phosphate: PO43-
Phosphite: PO33-
Ammonium: NH41+
Know Table 9.3 on page 257
If the polyatomic ion begins with H, then combine the word hydrogen with the other polyatomic ion present: H1+ + CO3
2- → HCO3
1-
hydrogen + carbonate → hydrogen carbonate ion
(One of the few positive polyatomic ions)
Writing Ionic Compound Formulas
Example: Barium nitrate (note the 2 word name)
1. Write the formulas for the cation and anion, including CHARGES!
Ba2+ NO3-
2. Check to see if charges are balanced. 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Use the criss-cross method to balance subscripts.
Not balanced!
( ) 2
Now balanced.
= Ba(NO3)2
Writing Ionic Compound Formulas
Example: Ammonium sulfate (note the 2 word name)
1. Write the formulas for the cation and anion, including CHARGES!
NH4+ SO4
2-
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Use the criss-cross method to balance the subscripts.
Not balanced!
( )2
Now balanced.
= (NH4)2SO4
Writing Ionic Compound Formulas
Example: Iron (III) chloride (note the 2 word name)
1. Write the formulas for the cation and anion, including CHARGES!
Fe3+Cl-
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Use the criss-cross method to balance the subscripts.
Not balanced!
3
Now balanced.= FeCl3
Writing Ionic Compound Formulas
Example: Aluminum sulfide (note the 2 word name)
1. Write the formulas for the cation and anion, including CHARGES!
Al3+ S2-
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Use the criss-cross method to balance the subscripts.
Not balanced!
2 3
Now balanced.= Al2S3
Writing Ionic Compound Formulas
Example: Magnesium carbonate (note the 2 word name)1. Write the formulas for the cation and anion, including CHARGES!
Mg2+CO32-
2. Check to see if charges are balanced.
They are balanced!
= MgCO3
Writing Ionic Compound Formulas
Example: Zinc hydroxide (note the 2 word name)
1. Write the formulas for the cation and anion, including CHARGES!
Zn2+ OH-
2. Check to see if charges are balanced. 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Use the criss-cross method to balance the subscripts.
Not balanced!
( )2
Now balanced.= Zn(OH)2
Writing Ionic Compound Formulas
Example: Aluminum phosphate (note the 2 word name)
1. Write the formulas for the cation and anion, including CHARGES!
Al3+ PO43-
2. Check to see if charges are balanced.
They ARE balanced!
= AlPO4
Naming Ionic CompoundsNaming Ionic Compounds 1. Name the cation first, then anion
2. Monatomic cation = name of the element
Ca2+ = calcium ion
3. Monatomic anion = root + -ide
Cl- = chloride
CaCl2 = calcium chloride
Naming Ionic CompoundsNaming Ionic Compounds
some metals can form more than one charge (usually the transition metals)
use a Roman numeral in their name:
PbCl2 – use the anion to find the charge
on the cation (chloride is always 1-)
Pb2+ is the lead (II) cation
PbCl2 = lead (II) chloride
(Metals with multiple oxidation states)
Things to look for:
1) If cations have ( ), the number in parenthesis is their charge.
2) If anions end in -ide they are probably off the periodic table (Monoatomic)
3) If anion ends in -ate or –ite, then it is polyatomic
Practice by writing the formula or name as required…
Iron (II) PhosphateStannous FluoridePotassium SulfideAmmonium ChromateMgSO4
FeCl3