Ionic Bonding Part I

An Elemental Love Story

Demo

Burning string demo Clean string vs Sugar soaked string vs Salt

soaked string Any difference?

Research Mission

For this week, you will read articles about: Iodine deficiency disorder Pros and cons of fluoride The importance of potassium The dangers of chromium

After gathering information, your group will present what you learned and how it relates to ions and ionic bonding.

Before we dive in

What is a chemical bond? What are three main different types of

bonds? Why do elements form ions? What is a cation? What is an anion?

Q: How do elements combine to form compounds?

A: Compounds have different forces that hold groups of atoms together and make them function as a unit called bonds.

Bonds

Bonds

Bonds come in three main varieties:

1. Metallic bonds – when metal cations bond they share a sea of delocalized electrons.

2. Ionic bonds – transfer of electrons between metals and non metals

3. Covalent bonds – sharing of electrons between two nonmetals

Metallic Bonding

Strong forces of attraction are responsible for the high melting point of most metals.

Metallic Bonding The chemical bonding that

results from the attraction between metal cations and the surrounding sea of electrons

Vacant p and d orbitals in metal's outer energy levels overlap, and allow outer electrons to move freely throughout the metal

Valence electrons do not belong to any one atom

Properties of Metals

Metals are good conductors of heat and electricity

Metals are malleable

Metals are ductile

Metals have high tensile strength

Metals have luster

Metal Alloys Alloys: some metal atoms replaced by

others of similar size.

Ionic bonding

Ionic compounds bond in repeating 3-dimensional patterns with alternating positive and negative ionscalled crystal lattice.

Ionic Crystal Lattice Shapes

Ionic bondingAll salts are ionic compounds and form crystals.

NaCl forms the simplest cubic structure

Properties of Ionic Compounds

Structure: Crystalline solids

Melting point:

Generally high

Boiling Point:

Generally high

Electrical Conductivity:

Excellent conductors, molten and aqueous

Solubility in water:

Generally soluble

Properties of Ionic Compounds

Lab! We will be examining the properties of ionic

compounds next double with a lab. In the meantime, we will move onto how and

why ions bond.

Great BBC video on ions

http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/atomic/ionicact.shtml

Know our ions inside and out

In order to be successful with ionic bonding, you need to know what ion each element in the s and p block will form.

Practice on the Ion worksheet grid in the packet

The Octet Rule – Ionic Compounds

Ionic compounds form so that each atom, by gaining or losing electrons, has an octet of electrons in its highest occupied energy level.

Ionic bonds form between metals and nonmetals!

• Metals lose electrons to form positively-charged cations

• Nonmetals gains electrons to form negatively-charged anions

Ionic Bonding:Sodium Chloride Example

Sodium has 1 valence electron

Cl: 1s22s22p63s23p5

Na: 1s22s22p63s1

Chlorine has 7 valence electrons

An electron transferred gives each an octet

Ionic Bonding

Cl- 1s22s22p63s23p6

Na+ 1s22s22p6

This transfer forms ions, each with an octet:

Ionic Bonding:Sodium Chloride Example

Cl- Na+

The resulting ions come together due to electrostatic attraction (opposites attract):

The net charge on the compound must equal zero

Ionic Bonding:Sodium Chloride Example

Writing Ionic Compounds with Electron Dot Diagrams

Drawing Ionic compounds

How would these elements bond?

Li F K Br

Drawing Ionic Compounds

Not all relationships are 1:1 with sharing of valence electrons.

Sometimes you need more of one element than the other to make a neutral compound

Drawing Ionic Compounds

How would these elements bond?

Mg Br

Draw the ionic compounds

How about

K S

Criss Cross method!

Example: Aluminum sulfide

1. Write the formulas for cation and anion, including CHARGES!

2. Do charges balance?3. If not, use criss-cross

method to balance subscripts.

Al3+ S2-

Not balanced!

2 3

Now balanced.

= Al2S3

Criss Cross Method!Example: Beryllium chloride

1. Write the formulas for cation and anion, including CHARGES!

Be2+Cl-

2. Do charges balance?

3. Balance charges, if necessary, using subscripts. Use criss-cross method to balance subscripts.

Not balanced!

2Now balanced.

= BeCl2

Mg Cl

Na O

Magnesium chloride: Magnesium loses two electrons and each chlorine gains one electron

Sodium oxide: Each sodium loses one electron and the oxygen gains two electrons

Al SAluminum sulfide: Each aluminum loses two electrons (six total) and each sulfur gains two electrons (six total)

Try the criss cross method

Naming Ionic Compounds

You may have noticed that the name of the nonmetal in the previous compounds sounded different (chloride instead of chlorine, oxygen inside of oxide) Can you think of what might be a naming rule for

ionic compounds? What’s the order we use? Do any of the names change?

Naming Ionic Compounds

Name the cation first and then the anion

Cations – use the name of the element

Anions – use the name of the nonmetal but change the ending to an –ide

Metal Monatomic Cations

Ion name

Lithium Li+ LithiumSodium Na+ SodiumPotassium K+ PotassiumMagnesium Mg2+ Magnesiu

mCalcium Ca2+ CalciumBarium Ba2+ BariumAluminum Al3+ Aluminum

Nonmetal Monatomic Anions

Ion Name

Fluorine F- Fluoride

Chlorine Cl- Chloride

Bromine Br- Bromide

Iodine I- Iodide

Oxygen O2- Oxide

Sulfur S2- Sulfide

Nitrogen N3- Nitride

Phosphorus P3- Phosphide

Practice!

Let’s try writing our predicting ion charges and and writing ionic compounds using the criss cross method

Ionic Bonding Wrinkles

Polyatomic molecules and

METALS WITH MULTIPLE IONS

Polyatomic ions

Many ionic compounds contain polyatomic ions which are ions made up of more than one atom.

Polyatomic ions are atoms that are covalently bonded together and act as an individual ion.

Because it exists as a unit, DO NOT change the subscripts within the ion.

In Ionic Compounds, you put ( ) around them

Polyatomic ions

You will not be asked to memorize the polyatomic ions, but…

You do need to be able to recognize them And use a resource to determine its ionic

charge So that you can balance and write ionic

compounds! http://www.youtube.com/watch?v=MJZeZvDx

cx8

Polyatomic Ion Names

CO3 2- carbonate OH – hydroxide SO4 2- sulfate

PO4 3- phosphate

NO3– nitrate

ClO3– chlorate

NH4 + ammonium

Writing Ionic Compound with polyatomics

Example: Zinc hydroxide

1. Write the formulas for cation and anion, including CHARGES!

Zn2+ OH-

2. Do charges balance?

3. Balance charges , if necessary, using subscripts. Use () if more than one polyatomic ion. Use criss-cross method to balance subscripts.

Not balanced!

( )2

Now balanced.

= Zn(OH)2

Example: Barium nitrate

1. Write the formulas for cation and anion, including CHARGES!

Ba2+ NO3-2. Do charges balance?

3. Balance charges , if necessary, using subscripts. Use () if more than one polyatomic ion. Use criss-cross method to balance subscripts.

Not balanced!

( ) 2Now balanced.

= Ba(NO3)2

Writing Ionic Compound with polyatomic molecules

Example: Ammonium sulfate (note the 2 word name)

NH4+ SO4

2-

2. Do charges balance? Not balanced!

( )2

Now balanced.

= (NH4)2SO43. Balance charges , if necessary, using subscripts. Use () if more than one polyatomic ion. Use criss-cross method to balance subscripts.

1. Write the formulas for cation and anion, including CHARGES!

METALS WITH MULTIPLE IONS

Up until now, we’ve only been working with ions from the s and p block and ignoring d-block

This is because d-block metals as well as other metals can often form more than one type of ion

Again, you will not have to memorize these ions, but be able to use a resource to write ionic compounds with them.

METALS WITH MULTIPLE IONS

For those metals it is important to represent which ion it is with a roman numeral.

If it is +1 you put a (I) after the name of the metal If it is +2 it is a (II) after the name of the metal If it is a +3, you put a (III) after the name of the

metal You include this roman numeral in the name

ONLY for metals that form multiple ions!

For example: NiBr2 would be Nickel (II) Bromide

Roman numeral review!

VI II III

IV VII II

I III V

Practice!

Now, let’s practice writing ionic compounds with either polyatomic ions or METALS WITH MULTIPLE IONS