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IONIC BONDS & IONIC FORMULAS
IONIC BONDS & IONIC FORMULAS
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 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
► Octet rule is satisfied!► Outermost s and p orbitals are filled.
► Ionic Compound – compound containing ionic bonds► Sodium chloride
► NaCl – Chemical Formula
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
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 – MgCl2
• Changing the subscript in a correctly written chemical formula will change the formula so that it no longer represents the compound
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.
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
IONIC FORMULAS
IONIC FORMULAS
Calcium Fluoride
Aluminum Oxide
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.
Charge
Subscript
IONIC FORMULAS – CRISS-CROSS
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• CO3
2- - Carbonate• SO4
2- - Sulfate• PO4
3- - Phosphate
• There are many more and they can be located on the handout!
POLYATOMIC IONS
Sulfate - SO42-
Hydroxide - OH-
Carbonate - CO32-
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+
• Phosphate: PO43-
• 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 using transition metals in ionic formulas, the name must 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
