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Ionic Bonding

Formation of Ions

Ions formed when atoms gain or lose

valence e- to achieve a stable octet

Cation – Positively charged ion

– Forms when atom loses electrons

Anion – negatively charged ion

– Forms when atom gains electrons

Naming Ions

Naming

– Metal as is (Sodium ion)

– non-metal with –ide suffix (chloride)

Monatomic Ions + Transition Metals

Monatomic ion = single atom with +/- charge

Transition Metals – always cations

– Use Roman numerals (stock system) to denote

charge:

• For Fe+, cation name = iron(I)

• For Fe2+

, cation name = iron(II)

• For Fe3+

, cation name = iron(III)

– There are classical names for metals with –ous

and –ic endings.

Polyatomic Ions

Polyatomic ion = a charged species

form from two or more atoms covalently

bonded

– Cation: NH4+ (ammonium)

– Anions: NO3- (nitrate), OH- (hydroxide)

Acts as a unit– NEVER change its

structure!

Most names end in –ate or –ite suffixes

Naming Ionic Compounds • Ionic compound

• Made of metal + nonmetal

• Transfer electrons from metal to nonmetal

• Always electrically neutral

Two parts - Cation and Anion

– Cation • Always listed first

• Use name of element

– Anion • Monatomic Anion – use –ide suffix on element name

• Polyatomic Anion – use name

NaCl Cation Anion

Naming Ionic Compounds For Transition Metals

– Use Roman numerals in name to denote

charge of cation OR use classical name

– Example: • FeCl

2 is iron (II) chloride or ferrous chloride

• FeCl3 is iron (III) chloride or ferric chloride

NaCl Sodium chloride

K2O Potassium oxide

Na2SO4 Sodium sulfate

Cu(NO3)2 Copper (II) nitrate

How Atoms make Compounds

When elements react with each

other:

–Atoms must collide with others

and then bond together

–Collisions are between electron

clouds not the nuclei of the

atoms

Ionic Bonding – Transfer of e-

Sodium (Na = 1 e-, 1s22s22p63s1) collides

with chlorine (Cl = 7 e-, 1s22s22p63s23p5) to

form sodium chloride (salt).

BAM - Na’s 1 e- transferred to Cl →

– Na has 11 p+, and 10 e- → Na+ ion

– Cl has 17 p+, and 18 e- → Cl- ion

Na+ strongly electrically attracted to Cl-, forms

ionic compound NaCl (salt)

Cl 8 e- [Ar]

Na 8 e- [Ne]

+ -

Formulas

Formula = unique designation of how a compound (ionic or covalent) is made up of elements

Subscripts - how many of each type of atom

– No subscript shown - only one atom of element

– Example: NaCl - one Na atom and one Cl atom

– Example: AlBr3 - one Al atom and three Br atoms

Formula unit - simplest ratio of atoms

in formula

– Example: CaCl2, Ca2Cl4, and Ca3Cl6

are all calcium chloride.

– CaCl2 = simplest ratio = best formula

for calcium chloride.

Ways To Write An

Ionic Formula

Charge

Balance

Ionic Bonding

Charge Balance Method

Ca + + P -

- -

Calcium has two positives

Phosphorus has three

negatives

Ionic Bonding

Charge Balance Method

Ca + + P -

- -

Ca + +

Need to bring in

another Ca to

balance out P BUT…Ca is not

balanced now!

Ionic Bonding

Charge Balance Method

Ca + + P

- - -

Ca + +

Need to

bring in

another

P to

balance

out Ca BUT…P is not

balanced now!

P - -

-

Ionic Bonding

Charge Balance Method

Ca + + P

- - -

Ca + +

Need to

bring in

another

Ca to

balance

out P P - -

-

Ca + + NOW It is all balanced !

Ionic Bonding

Ca3P2

Formula Unit

Ways To Write An

Ionic Formula

Crisscross

Method

Ionic Bonding

Ca+2 P-3

Crisscross Method

Need the least common denominator

(3) = 6 (2) = 6

Ionic Bonding

Ca+2 P-3

Crisscross Method

Just crisscross charges…they

become subscripts

2 3

Ionic Bonding

Ca P

Crisscross Method

Tells you how many of each you

need

3 2

Ionic Bonding

Ca3P2

Formula Unit

Balancing Ionic Charge

Criss-Cross method - simple way of

writing names of neutral ionic

compounds

Cation charge # Anion subscript

Anion charge # Cation subscript

Polyatomic Ions = use parenthesis

– Aluminum Sulfate = Al2(SO4)3

Al3+ O2-

Al2O3 Al3+ O2-

Criss-Cross Polyatomic Ions

NEVER EVER

CHANGE A SUBSCRIPT

OF A POLYATOMIC ION!

USE PARENTHESES TO SHOW THE NUMBER OF POLYATOMIC IONS! Al3+SO4

2- → Al2(SO4)3

Electron Dot diagrams

A way of keeping track of

valence electrons.

Write the symbol.

Put one dot for each

valence electron

Don’t pair up until they

have to

X

The Electron Dot diagram for

Nitrogen Nitrogen has 5 valence

electrons.

First we write the symbol.

N Then add 1 electron at a

time to each side.

Then pair up.

Lewis Dot Diagrams (Electron Dot

Structure)

Lewis Dot Diagrams show

valence e’s on elements that

are not transition metals

Only the outermost s- and p-

orbital electrons

Lewis Dot Diagrams Draw the Lewis Dot Diagrams for the

following elements:

O 1s22s22p4 Cl [Ne]3s23p5 Cl O

P 1s22s22p63s23p3 Li 1s22s1 Li

Ne 1s22s22p6 Ca [Ar]4s2 Ne Ca

P

Electron Dots For Ions

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.

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.

Properties of Ionic Compounds

NaCl forms a very regular structure:

– Each Na+ ion surrounded by 6 Cl- ions

– Each Cl- ion is surrounded by six Na+

ions

– Ions packed as closely as possible

Most ionic compounds are:

– Crystalline solids at room temperature

– Have high melting points

– Dissolve into ions in water

– Conduct electrical current when

dissolved in water

Crystalline structure

Called Crystal Lattice

Do they Conduct? Conducting electricity is allowing charges

to move.

In a solid, the ions are locked in place.

Ionic solids are insulators.

How can we get them to

conduct? Melt them!

Dissolve in water!

Ionic solids are brittle

+ - + - + - + -

+ - + - + - + -

Ionic solids are brittle

+ - + - + - + -

+ - + -

Strong Repulsion breaks crystal apart.

Metallic Bonds How atoms are held together in the solid.

Metals hold onto their valence electrons very

weakly.

Think of them as positive ions floating in a

sea of electrons.

Malleability, ductility, conductibility

Sea of Electrons

+ + + +

+ + + +

+ + + +

Electrons are free to move through the

solid.

Metals conduct electricity.

Malleable

+ + + +

+ + + +

+ + + +

Electrons allow atoms to slide by.

Malleable/Ductile

+ + + +

+ + + +

+ + + +

Hammered into shape (bend).

Ductile - drawn into wires.

Bonding in Metals Metallic objects (like copper wire) are

made up of closely packed atoms

– Crystalline structure (like ionic

compounds)

– Valence e- can be modeled as a sea of

electrons, with nucleus + core electrons

acting like cations • Valence e- are free to move!

Alloy = homogenous mixture of metals

– Mixture is superior to base metals’

properties

Practice

Sodium Ion

– Na+

Phosphide ion

– P3-

Chloride Ion

– Cl-

Strontium ion

– Sr2+

Practice

Pb2+

– Lead(II) ion

Sn4+

– Tin(IV) ion

Be2+

– Beryllium ion

S2-

– Sulfide ion

Practice

Carbonate

– CO32-

Cyanide

– CN-

NH4+

– ammonium

OH-

– hydroxide

Mixed Practice

Beryllium chloride

– BeCl2

LiF

– Lithium fluoride

Sr3(PO4)2

– Strontium phospate

Calcium acetate

– Ca(C2H3O2)2