Chapter 7 “Ionic and Metallic Bonding” 7.1 - Ions

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


Example: Ammonium sulfate (note the 2 word name)


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


Example: Iron (III) chloride (note the 2 word name)


Fe3+Cl-



Not balanced!

3

Now balanced.= FeCl3


Example: Aluminum sulfide (note the 2 word name)


Al3+ S2-



Not balanced!

2 3

Now balanced.= Al2S3


Example: Magnesium carbonate (note the 2 word name)1. Write the formulas for the cation and anion, including CHARGES!

Mg2+CO32-


They are balanced!

= MgCO3


Example: Zinc hydroxide (note the 2 word name)


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


Example: Aluminum phosphate (note the 2 word name)


Al3+ PO43-


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

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Chapter 7 “Ionic and Metallic Bonding” 7.1 - Ions