IONIC BONDS & IONIC FORMULAS

Transcription

1 IONIC BONDS & IONIC FORMULAS

2 BONDING CHEMICAL BONDING Chemical bond an attraction between 2 atoms involving their valence electrons Ionic bond -chemical bond resulting from the electrostatic attraction between positive and negative ions (+ and -) Between a cation and an anion, or a metal and nonmetal There is a transferof electrons between the two atoms!! Cations are positive (+) Anions are negative (-) Opposites attract!!

3 IONIC BOND Sodium loses an electron Chlorine gains that electron Octet rule is satisfied! Outermost s and p orbitals are filled. Ionic Compound compound containing ionic bonds Sodium chloride NaCl Chemical Formula

4 IONIC COMPOUND Ionic Compound crystal lattice of cation atoms surrounded by anion atoms 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

5 CHEMICAL FORMULA Chemical formula shorthand representation of the composition of a substance using atomic symbols and numerical subscripts Subscript number of atoms of that element Magnesium Chloride MgCl 2 Changing the subscript in a correctly written chemical formula will change the formula so that it no longer represents the compound

6 IONIC CHEMICAL FORMULAS 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.

7 IONIC COMPOUND 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

8 IONIC FORMULAS

9 IONIC FORMULAS Calcium Fluoride Aluminum Oxide

10 IONIC FORMULAS Try creating an ionic formula for: Sodium and Oxygen Then name it! Na 2 O Sodium Oxide

11 IONIC FORMULAS CRISS-CROSS Subscript The neutral ionic compound can also be created by taking the CHARGE of the ions and criss-crossing to form the SUBSCRIPT. Charge

12 IONIC FORMULAS CRISS-CROSS

13 SIMPLIFY SUBSCRIPTS

14 VARIABLE CHARGE CATIONS Transition metals in ionic compounds are able to lose different numbers of electrons to create their ions. When writing transition metals in ionic formulas, we must always include a roman numeralafter the transition metal, or cation, to indicate its charge.

15 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)

16 ROMAN NUMERALS

17 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 CuCl 2.

18 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, SnCl 4 : 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

19 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!!!

20 POLYATOMIC IONS Some of the polyatomic ions you will see: NH 4+ -Ammonium OH - -Hydroxide NO 3- -Nitrate CO 2-3 -Carbonate SO 2-4 -Sulfate PO 3-4 -Phosphate There are many more and they can be located on the handout!

21 POLYATOMIC IONS Carbonate -CO 3 2- Sulfate -SO 4 2- Hydroxide -OH -

22 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 parenthesesto indicate that we have that many of the WHOLE polyatomic ion!!! The polyatomic MUST stay together as a GROUP! Magnesium Hydroxide MgOH 2 WRONG Mg(OH) 2 CORRECT!

23 TERNARY IONIC COMPOUNDS Calcium Phosphate: Calcium: Ca 2+ Phosphate: PO 3-4 Ca 3 (PO 4 ) 2 Try these: Sodium Carbonate Na 2 CO 3 Aluminum Hydroxide Al(OH) 3