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Ionic Bonding
Formation of Ions
Ions formed when atoms gain or lose
valence e- to achieve a stable octet
Cation – Positively charged ion
– Forms when atom loses electrons
Anion – negatively charged ion
– Forms when atom gains electrons
Naming Ions
Naming
– Metal as is (Sodium ion)
– non-metal with –ide suffix (chloride)
Monatomic Ions + Transition Metals
Monatomic ion = single atom with +/- charge
Transition Metals – always cations
– Use Roman numerals (stock system) to denote
charge:
• For Fe+, cation name = iron(I)
• For Fe2+
, cation name = iron(II)
• For Fe3+
, cation name = iron(III)
– There are classical names for metals with –ous
and –ic endings.
Polyatomic Ions
Polyatomic ion = a charged species
form from two or more atoms covalently
bonded
– Cation: NH4+ (ammonium)
– Anions: NO3- (nitrate), OH- (hydroxide)
Acts as a unit– NEVER change its
structure!
Most names end in –ate or –ite suffixes
Naming Ionic Compounds • Ionic compound
• Made of metal + nonmetal
• Transfer electrons from metal to nonmetal
• Always electrically neutral
Two parts - Cation and Anion
– Cation • Always listed first
• Use name of element
– Anion • Monatomic Anion – use –ide suffix on element name
• Polyatomic Anion – use name
NaCl Cation Anion
Naming Ionic Compounds For Transition Metals
– Use Roman numerals in name to denote
charge of cation OR use classical name
– Example: • FeCl
2 is iron (II) chloride or ferrous chloride
• FeCl3 is iron (III) chloride or ferric chloride
NaCl Sodium chloride
K2O Potassium oxide
Na2SO4 Sodium sulfate
Cu(NO3)2 Copper (II) nitrate
How Atoms make Compounds
When elements react with each
other:
–Atoms must collide with others
and then bond together
–Collisions are between electron
clouds not the nuclei of the
atoms
Ionic Bonding – Transfer of e-
Sodium (Na = 1 e-, 1s22s22p63s1) collides
with chlorine (Cl = 7 e-, 1s22s22p63s23p5) to
form sodium chloride (salt).
BAM - Na’s 1 e- transferred to Cl →
– Na has 11 p+, and 10 e- → Na+ ion
– Cl has 17 p+, and 18 e- → Cl- ion
Na+ strongly electrically attracted to Cl-, forms
ionic compound NaCl (salt)
Cl 8 e- [Ar]
Na 8 e- [Ne]
+ -
Formulas
Formula = unique designation of how a compound (ionic or covalent) is made up of elements
Subscripts - how many of each type of atom
– No subscript shown - only one atom of element
– Example: NaCl - one Na atom and one Cl atom
– Example: AlBr3 - one Al atom and three Br atoms
Formula unit - simplest ratio of atoms
in formula
– Example: CaCl2, Ca2Cl4, and Ca3Cl6
are all calcium chloride.
– CaCl2 = simplest ratio = best formula
for calcium chloride.
Ways To Write An
Ionic Formula
Charge
Balance
Ionic Bonding
Charge Balance Method
Ca + + P -
- -
Calcium has two positives
Phosphorus has three
negatives
Ionic Bonding
Charge Balance Method
Ca + + P -
- -
Ca + +
Need to bring in
another Ca to
balance out P BUT…Ca is not
balanced now!
Ionic Bonding
Charge Balance Method
Ca + + P
- - -
Ca + +
Need to
bring in
another
P to
balance
out Ca BUT…P is not
balanced now!
P - -
-
Ionic Bonding
Charge Balance Method
Ca + + P
- - -
Ca + +
Need to
bring in
another
Ca to
balance
out P P - -
-
Ca + + NOW It is all balanced !
Ionic Bonding
Ca3P2
Formula Unit
Ways To Write An
Ionic Formula
Crisscross
Method
Ionic Bonding
Ca+2 P-3
Crisscross Method
Need the least common denominator
(3) = 6 (2) = 6
Ionic Bonding
Ca+2 P-3
Crisscross Method
Just crisscross charges…they
become subscripts
2 3
Ionic Bonding
Ca P
Crisscross Method
Tells you how many of each you
need
3 2
Ionic Bonding
Ca3P2
Formula Unit
Balancing Ionic Charge
Criss-Cross method - simple way of
writing names of neutral ionic
compounds
Cation charge # Anion subscript
Anion charge # Cation subscript
Polyatomic Ions = use parenthesis
– Aluminum Sulfate = Al2(SO4)3
Al3+ O2-
Al2O3 Al3+ O2-
Criss-Cross Polyatomic Ions
NEVER EVER
CHANGE A SUBSCRIPT
OF A POLYATOMIC ION!
USE PARENTHESES TO SHOW THE NUMBER OF POLYATOMIC IONS! Al3+SO4
2- → Al2(SO4)3
Electron Dot diagrams
A way of keeping track of
valence electrons.
Write the symbol.
Put one dot for each
valence electron
Don’t pair up until they
have to
X
The Electron Dot diagram for
Nitrogen Nitrogen has 5 valence
electrons.
First we write the symbol.
N Then add 1 electron at a
time to each side.
Then pair up.
Lewis Dot Diagrams (Electron Dot
Structure)
Lewis Dot Diagrams show
valence e’s on elements that
are not transition metals
Only the outermost s- and p-
orbital electrons
Lewis Dot Diagrams Draw the Lewis Dot Diagrams for the
following elements:
O 1s22s22p4 Cl [Ne]3s23p5 Cl O
P 1s22s22p63s23p3 Li 1s22s1 Li
Ne 1s22s22p6 Ca [Ar]4s2 Ne Ca
P
Electron Dots For Ions
Ionic Bonding
Anions and cations are held together by
opposite charges.
Ionic compounds are called salts.
Simplest ratio is called the formula unit.
The bond is formed through the transfer
of electrons.
Electrons are transferred to achieve
noble gas configuration.
Properties of Ionic Compounds
Crystalline structure.
A regular repeating arrangement of ions
in the solid.
Ions are strongly bonded.
Structure is rigid.
High melting points- because of strong
forces between ions.
Properties of Ionic Compounds
NaCl forms a very regular structure:
– Each Na+ ion surrounded by 6 Cl- ions
– Each Cl- ion is surrounded by six Na+
ions
– Ions packed as closely as possible
Most ionic compounds are:
– Crystalline solids at room temperature
– Have high melting points
– Dissolve into ions in water
– Conduct electrical current when
dissolved in water
Crystalline structure
Called Crystal Lattice
Do they Conduct? Conducting electricity is allowing charges
to move.
In a solid, the ions are locked in place.
Ionic solids are insulators.
How can we get them to
conduct? Melt them!
Dissolve in water!
Ionic solids are brittle
+ - + - + - + -
+ - + - + - + -
Ionic solids are brittle
+ - + - + - + -
+ - + -
Strong Repulsion breaks crystal apart.
Metallic Bonds How atoms are held together in the solid.
Metals hold onto their valence electrons very
weakly.
Think of them as positive ions floating in a
sea of electrons.
Malleability, ductility, conductibility
Sea of Electrons
+ + + +
+ + + +
+ + + +
Electrons are free to move through the
solid.
Metals conduct electricity.
Malleable
+ + + +
+ + + +
+ + + +
Electrons allow atoms to slide by.
Malleable/Ductile
+ + + +
+ + + +
+ + + +
Hammered into shape (bend).
Ductile - drawn into wires.
Bonding in Metals Metallic objects (like copper wire) are
made up of closely packed atoms
– Crystalline structure (like ionic
compounds)
– Valence e- can be modeled as a sea of
electrons, with nucleus + core electrons
acting like cations • Valence e- are free to move!
Alloy = homogenous mixture of metals
– Mixture is superior to base metals’
properties
Practice
Sodium Ion
– Na+
Phosphide ion
– P3-
Chloride Ion
– Cl-
Strontium ion
– Sr2+
Practice
Pb2+
– Lead(II) ion
Sn4+
– Tin(IV) ion
Be2+
– Beryllium ion
S2-
– Sulfide ion
Practice
Carbonate
– CO32-
Cyanide
– CN-
NH4+
– ammonium
OH-
– hydroxide
Mixed Practice
Beryllium chloride
– BeCl2
LiF
– Lithium fluoride
Sr3(PO4)2
– Strontium phospate
Calcium acetate
– Ca(C2H3O2)2