Part I – Ionic bonding An Elemental Love Story

Before we dive in What is a chemical bond? What are three main different types of bonds? What are some properties of these different types of bonds?

Bonding 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.

Bonding Bonds come in three main varieties: Ionic bonds – transfer of electrons between metals and non metals Metals & Metallic bonds – when metal cations bond they share a sea of delocalized electrons. Covalent bonds – sharing of electrons between two nonmetals

Demo Let’s compare two of those types of bonds – ionic and covalent Which do you think is stronger? How might we tell which are stronger? Burning string demo Plain string vs sugar soaked string vs salt soaked string Any difference?

Ions and Ionic Bonds Clearly ionic bonding is very strong!

Ion 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.

Great BBC video on ions http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/atomic/ionicact.shtml

Ionic bonding Bonds that form between oppositely charged ions Ionic bonds form between metals and nonmetals! Metals become positive ions (cations) and nonmetals become negative ions (anions) Opposites attract! This attraction forms an Ionic bond and each then are left with a complete octet!

Properties of Ionic Compounds Structure: Crystalline solids Melting point: Generally high Boiling Point: Electrical Conductivity: Excellent conductors, molten and aqueous Solubility in water: Generally soluble

Ionic Bonding: Sodium Chloride Example Sodium has 1 valence electron Chlorine has 7 valence electrons An electron transferred gives each an octet Na: 1s22s22p63s1 Cl: 1s22s22p63s23p5

Ionic Bonding

Ionic Bonding: Sodium Chloride Example This transfer forms ions, each with an octet: Na+ 1s22s22p6 Cl- 1s22s22p63s23p6

Ionic Bonding: Sodium Chloride Example The resulting ions come together due to electrostatic attraction (opposites attract): Na+ Cl- The net charge on the compound must equal zero

Writing Ionic Compounds with Electron Dot Diagrams

Drawing Ionic compounds How would these elements bond? Li F K Br

Drawing Ionic Compounds Unlike our atomic dating game…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

Interactive – Ionic bonding http://www.learner.org/interactives/periodic/groups_interactive.html Write the ions formed and then the ionic compound formulas Can you see a pattern?

Al3+ S2- Criss Cross method! 2 3 = Al2S3 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- 2 3 Not balanced! Now balanced. = Al2S3

Be2+ Cl- Criss Cross Method! 2 = BeCl2 Example: Beryllium chloride 1. Write the formulas for cation and anion, including CHARGES! Be2+ Cl- 2 Now balanced. 2. Do charges balance? Not balanced! 3. Balance charges, if necessary, using subscripts. Use criss-cross method to balance subscripts. = BeCl2

Mg Cl Na O Al S Try the criss cross method Magnesium chloride: Magnesium loses two electrons and each chlorine gains one electron Mg Cl Sodium oxide: Each sodium loses one electron and the oxygen gains two electrons Na O Aluminum sulfide: Each aluminum loses two electrons (six total) and each sulfur gains two electrons (six total) Al S

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+ Sodium Na+ Potassium K+ Magnesium Mg2+ Calcium Ca2+ Barium Ba2+ Aluminum Al3+

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

Try some on your own Cl - S 2- As 3- Li+ Li+ Cl - LiCl Mg 2+ Al 3+ Lithium chloride Mg 2+ Al 3+

Ionic Bonding Wrinkles Polyatomic molecules

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 find it useful to remember a few polyatomic ions that we use repeatedly So that you can balance and write ionic compounds! Tyler Dewitt (5:15) http://www.youtube.com/watch?v=MJZeZvDxcx8

Polyatomic Ion Names NH4 + ammonium -1 -2 -3 OH – hydroxide NO3– nitrate CN – cyanide CO3 2- carbonate SO4 2- sulfate PO4 3- phosphate

Writing Ionic Compound with polyatomics Example: Zinc hydroxide 1. Write the formulas for cation and anion, including CHARGES! ( ) Zn2+ OH- 2 Now balanced. 2. Do charges balance? Not balanced! 3. Balance charges , if necessary, using subscripts. Use () if more than one polyatomic ion. Use criss-cross method to balance subscripts. = Zn(OH)2

( ) Ba2+ NO3- 2 = Ba(NO3)2 Example: Barium nitrate 1. Write the formulas for cation and anion, including CHARGES! ( ) Ba2+ NO3- 2. Do charges balance? 2 3. Balance charges , if necessary, using subscripts. Use () if more than one polyatomic ion. Use criss-cross method to balance subscripts. Now balanced. Not balanced! = Ba(NO3)2

Writing Ionic Compound with polyatomic molecules Example: Ammonium sulfate (note the 2 word name) ( ) NH4+ SO42- 1. Write the formulas for cation and anion, including CHARGES! 2 Now balanced. 2. Do charges balance? Not balanced! = (NH4)2SO4 3. Balance charges , if necessary, using subscripts. Use () if more than one polyatomic ion. Use criss-cross method to balance subscripts.

Try some on your own CO3 2- OH - SO4 2- PO4 3- Na+ Na+ (CO3) 2- Sodium carbonate NH4 + Ca 2+ Ca 2+ (CO3) 2- Ca(CO3) Calcium carbonate Al 3+

Ionic Bonding Wrinkles TIME TO TALK ABOUT THOSE TRANSITION D BLOCK METALS WE’VE BEEN AVOIDING!

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 Transition Metals Metals have high melting points. Metals are good conductors of heat and electricity Metals are malleable Metals are ductile Metals are strong Metals have luster

ELECTRONS IN TRANSITION METALS Up until now we have only talked about ions from the s and p block. This is because transition metals can be tricky. Since d-orbital electrons are held less tightly than s and p orbitals, Almost all transition metals can become ions with multiple charges.

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 I V

Look at your periodic table Only three transition metals have a constant charge. It will be handy for you to remember those since you should NOT use a roman numeral for those! Zinc +2 Silver +1 Cadmium

Let’s try some Br - O2- P 3- CO3 2- Pb+2 Pb+2 (CO3) 2- Pb(CO3) Lead (II) carbonate Cu + Zn 2+ Zn 2+ (CO3) 2- Zn(CO3) Zinc carbonate Co 3+

Practice! Now, let’s practice pull it all together