Review Questions  On your own, complete the 14 review questions  You may use the internet or your notes to complete them.

Polyatomic Ions  A polyatomic ion is a charged chemical ion composed of two or more atoms covalently bonded that can be considered to be acting as a single unit.  Ions with a positive charge are called cations  Ions with a negative charge are called anions  These ions are frequently given specific names.  For example: Ammonia is NH 3 and is neutral but the Ammonium ion is NH 4 and has a charge of +1

Important Ions

Bonds  A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms.  Ionic bonding is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions.  A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms.

Bonds  A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms.  Ionic bonding is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions.  A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms.

Ionic versus Covalent

Naming Compounds  We name ionic and covalent compounds differently.  General rule for ionics: Metal first (cation), Non- metal (anion) second.  Example: Sodium and Chlorine become Sodium chloride  Example: Potassium and the Permanganate ion become Potassium Permanganate.  General rule for covalents: Use prefixes like mono, di, tri, etc.  Example: Carbon and 2 Oxygens become Carbon dioxide.  Example: 4 Sulfurs and 2 Chlorines become Tetrasulfur dichloride

Basic Info – Ionic Bonds  An ionic bond involves the transfer of electrons between a non-metal and a metal  These ions have electrostatic attraction.  Example : Sodium (cation – metal) and Chlorine (anion – non-metal)  Sodium has 1 valence electron. Chlorine has 7 valence electrons  Sodium “gives” its electron to chlorine  Compound is Sodium Chloride

More examples  Example : Barium and Bromine  Barium has _____ valence electron. Bromine has ____ valence electrons  How many bromines are needed per barium?

Trickier example  Example : Aluminum and a Sulfate ion  Aluminum has ______ valence electron(s) and an oxidation # of ___________.  Sulfate has an oxidation # of ______ (look at the list of polyatomic ions!)  How many Aluminums and Sulfates will be needed?  FIND THE LOWEST COMMON MULTIPLE…..

Lewis Dot Model  Also called Electron Dot Structures Models  Represent atoms and ions with dots representing the valence electrons  Typically only the s and p orbital = octet rule  Rules:  a) Metals should have dots only.  b) Non-metals have spaces and dots.  c) Period 1 atoms follow the duet rule and Periods 2 & 3 follow the octet rule.  Dot Models for Period 4-7 on are not very accurate because of the d and f orbitals

Examples  Phosphorus: Group 1 5 so 5 valence e’s  Non-metal, so would like 3 more e’s  Scandium: Group 3 so 3 valence e’s  Metal, so it would like to get rid of those e’s  Phosphorus would like 3 e’s, Scandium would like to get rid of 3 e’s  Scandium Phosphide

Naming Ionic Compounds  Binary – any compound with only 2 different elements.  The non-metal name is changed to end with -ide  Example: Calcium and Chlorine  Step 1. What are the oxidation numbers of Calcium and Chlorine  Step 2. Cross the oxidation numbers  Step 3. Name the compound (METAL then NON- METAL)  Calcium Chloride

More Practice  What is the name of the compound: NaFl  Oxidation # Na = ? Oxidation # Fl = ?  What is the name of the compound: FeO 2  Oxidation # Fe= ? Oxidation # O = ?  Determine the formulas:  Oxidation # Al = ? Oxidation # O = ?  Formula: Aluminum Oxide ?  Oxidation # Mg= ? Oxidation # S = ?  Formula: Magnesium Sulfide ?

Polyatomic Ions  Polyatomic ions are exceptions to the “ide” rule  Sodium hydroxide  What is hydroxide? What is its oxidation #?  What is sodium’s oxidation number?  Potassium permanganate  What is permanganate? What is its oxidation #?  What is potassium’s oxidation number?  Don’t change the way the polyatomic ion is written!

Writing the formula 1) Write the symbol for the first element… 2) Place the Oxidation # on the top of the element (VI) = 6 3) Name the polyatomic ion - sulfite – NOTICE MY PARENTHESIS 4) Put the two (metal first) side by side and crossover the charges 5) Question? What do we do with the 2 and the 6? Reduce….. Manganese (VI) Sulfite

More practice 1) Write the name for the first symbol… 2) Decide whether or not it needs parenthesis in the middle…all except Group 1+2, Al, Zn, Ag need ( ) 3) Write the name of the polyatomic ion – (B 4 O 7 ) 2- 4) To find the number in the ( ), we need to recognize the ratio of Chromium atoms to Tetraborate molecules 5) Since Tetraborate has ALWAYS got a 2- charge we need to… 6) As you can see, the 1 to 2 ratio became a 2 to 4 ratio and the 4 crosses back up top to give Cr a 4+ Oxidation # 7.) Report your final answer Example: Write the formal name of Cr(B 4 O 7 ) 2

Facts about Ionics  Ionic compounds form crystals  They have high melting and boiling points  Ionic compounds are hard and brittle  They conduct electricity when they are dissolved in water  These are called electrolytes or aqueous solutions  They don’t conduct electricity when they are solid

Facts about Ionics  Compounds having water attached are called hydrates or hydrous  Compounds that have no water are called anhydrous.  The chemistry storeroom has many compounds that absorb water over time. These are called hygroscopic Special compounds for industrial use that absorb water are called humectants.

Naming Hydrates  We name the ionic compound the same way but we add _______hydrate, where the blank is the number of waters.  1 = mono, 2 = di, 3 = tri, 4 = tetra, 5 = penta, 6 = hexa, 7 = hepta, 8 = octa, 9 = nona, 10 = deca  What is Ba(OH) 2 8H 2 O?

Acids  Acids are compounds that donate protons (Hydrogen ions) when in solution.  We will learn more about acids later.  Bases are compounds that accept protons  They often have an hydroxide ion in the compound  Most acids have a Hydrogen cation in as the first element in their chemical formula.  Safety: When diluting acids, chemists will always add the concentrated acid to water.  It makes the solution more dilute and less likely to release heat!

Rule 1  Acids with Hydrogen as the cation and a non- metal as the anion are named by adding HYDRO prefix to the front and an –ic suffix to the end.  Example : Hydrogen and Fluorine:  HF, called Hydrofluoric Acid  On your own:  Hydrosulfuric Acid  Hydroiodic Acid

Rule 2  Acids with Hydrogen as the cation and a polyatomic “ate” group as the anion are named by replacing the –ate suffix with an –ic suffix and adding the term acid at the end.  Example : Hydrogen and Carbonate  Formula for Carbonic Acid: H 2 (CO 3 )  On your own :  Sulfuric Acid  Nitric Acid  Oxalic Acid

Rule 3  Acids with Hydrogen as the cation and a polyatomic “ite” group as the anion are named by replacing the –ite suffix with an -ous suffix and adding the term acid at the end.  Example : Hydrogen and Carbonite: write the formula and oxidation number for carbonite:  Formula for Carbonous Acid: H 2 (CO 2 )  On your own :  Sulfurous Acid  Nitrous Acid

Rule 4 & 5  Rule 4 & 5 are for super-oxygen rich polyatomic ions called per______ates and for oxygen- depleted polyatomic ions called hypo______ites.

Electronegativity  Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons.  Scale goes from 0 to 4.0  Fluorine is the most electronegative atom  Francium is the least.

Differences in Electronegativity  When atoms prefer to bond when there is a large difference in electronegativity.  If the difference is greater than 1.8, then the bond is ionic and the electrons are transferred.  If the difference is less, then the bond is covalent and the electrons are shared.  The more equal the electronegativity values are, the more equally the electrons are shared.