Ionic Bonds & Ionic Formulas Bonding…Chemical Bonding

 Chemical bond – an attraction between 2 atoms

 Ionic bond - Formed between two atoms that gain and lose electrons  Between a cation and an anion, or a metal and nonmetal  There is a transfer of electrons between the two atoms!!

 Cations are positive (+)  Anions are negative (-)  Opposites attract!! Ionic Bond

 Sodium loses an electron  Chlorine gains that electron  Ionic Bonds involve a transfer of electrons!

 Ionic Compound – cation and an anion held together by their charge difference (+ and -)

 Sodium chloride (NaCl) Ionic Compound

 Ionic compounds properties:  High melting and boiling points  Solid at room temp  Usually hard and brittle  Not good conductors when in solid form  Good conductors when dissolved in water – ions can move and transfer electricity  Electrolytes Ionic Formulas

 Ionic formula – contains atoms and number of atoms involved in an ionic compound

 Ionic formulas always begin with the CATION or METAL.  POSITIVE FIRST!  Cations are named as their element name with ion after it.  Sodium becomes the Sodium ion.  Potassium becomes the Potassium ion.

 Ionic formulas end with the ANION or NONMETAL.  Anions are named by dropping the ending of their elemental name and adding –ide.  Oxygen becomes the Oxide ion.  Fluorine becomes the Fluoride ion.  Chlorine becomes the Chloride ion. Ionic Formulas

 We combine the cation and the anion to create an ionic compound  Binary Ionic Compound (2 elements!)

 Ionic compounds are electrically neutral so we have to find the correct ratio of positive to negative charges to create a neutral ionic compound.  Charges must = 0 Ionic Formulas

Calcium Fluoride

Aluminum Oxide Ionic Formulas Ionic Formulas

 Try creating an ionic formula for:  Sodium and Oxygen

 Then name it!

 Na2O – Sodium Oxide Ionic Formulas – Criss-Cross

 The neutral ionic compound can also be created by taking the CHARGE of the ions and criss-crossing to form the SUBSCRIPT.

Subscript

Charge Ionic Formulas – Criss-Cross Simplify Subscripts Polyatomic Ions

 In addition to the simple cations and anions (monatomic) we have, there are a set of more complicated ions called polyatomic ions.

 Polyatomic ion - ion made of many atoms  Poly = many!

 They will ALWAYS stay together as a group!!! Polyatomic Ions

 Some of the polyatomic ions you will see:

+  NH4 - Ammonium  OH- - Hydroxide -  NO3 - Nitrate 2-  CO3 - Carbonate 2-  SO4 - Sulfate 3-  PO4 - Phosphate

 There are many more and they can be located on the handout! Polyatomic Ions

2- Carbonate - CO3

2- Sulfate - SO4 Hydroxide - OH- Polyatomic Ions

 Polyatomic ions create ionic compounds and formulas just as the simple ions are, with one small difference.

 When they are in compounds that require a subscript on the polyatomic ion, we must include parentheses to indicate that we have that many of the WHOLE polyatomic ion!!!

 The polyatomic MUST stay together as a GROUP!

 Magnesium Hydroxide

 MgOH2  WRONG

 Mg(OH)2  CORRECT! Ternary Ionic Compounds

 Calcium Phosphate:  Calcium: Ca2+ 3-  Phosphate: PO4

 Ca3(PO4)2

 Try these:  Sodium Carbonate

 Na2CO3  Aluminum Hydroxide

 Al(OH)3 Variable Charge Cations

 Transition metals in ionic compounds are able to lose different numbers of electrons to create their ions.

 When naming transition metals in ionic formulas, we must always include a roman numeral after the transition metal, or cation, to indicate its charge. Variable Charge Cations

 Copper has 2 possible charges, +1 or +2.  Copper (I)  Copper (II)

 Manganese has 2 possible charges, +2 or +4.  Manganese (II)  Manganese (IV) Roman Numerals Variable Charge Cations

 In a compound, when writing the name, we ALWAYS have to include the charge when we have a transition metal.

 This will also give you the charge of the element to use when writing the ionic formula.

 For instance, Copper (II) Chloride:  This tells you that the charge on the Copper ion is +2 and we know that the charge on the Chloride ion is -1.

 The ionic formula here is CuCl2. Variable Charge Cations

 You may also have to find the name of a variable charge cation by using the formula.

 We will ALWAYS know the charge on the anion (negative).

 Use the anion charge to find the cation charge!

 For instance, SnCl4:  Chlorine has a charge of -1. There are 4 atoms of Chlorine: 4 x -1 = -4  The cation (positive) MUST balance the anion (negative).

 Anion = -4 so the cation = +4

 The name is Tin (IV) Chloride Variable Charge Cations

 For instance, SnCl4:  Chlorine has a charge of -1. There are 4 atoms of Chlorine: 4 x -1 = -4  The cation (positive) MUST balance the anion (negative).

 Anion = -4 so the cation = +4

Cl-1

+4 = +4 Cl-1 1 +4 Sn? -4 Cl-1

Cl-1