Ionic Bonding Topic 4.1

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Ionic BondingTopic 4.1
http//www.youtube.com/watch?vxTx_DWboEVs
http//www.youtube.com/watch?v5IJqPU11ngY
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Review

• Valence electrons
• electrons in the highest occupied energy level
• always in the s and p orbitals
• normally just a draw a circle to represent these
  two orbitals
• determines the chemical properties of an element
• usually the only electrons used in chemical bonds

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IB may group levels together and therefore you
would see the 3d10 before the 4s2
http//wps.prenhall.com/wps/media/objects/476/4883
16/Instructor_Resources/Chapter_09/FG09_27-06un.JP
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IB uses this one
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Lewis/Electron Dot Diagrams/Structures

• electron dot structures/diagrams are used to show
  valence electrons
• each dot around the element symbol represents a
  valence electron

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• B is 1s2 2s2 2p1
• 2 is the outermost energy level
• it contains 3 valence electrons, 2 in the s and 1
  in the p
• Br is Ar 4s2 3d10 4p5How many valence
  electrons are present?

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Ionic Charge

• when forming compounds, atoms tend to achieve the
  electron configuration of a noble gas (ns2np6)
• this means their highest energy level will be
  filled with 8 electrons that requires the least
  amount of energy
• cations
• atoms of metallic elements (groups 1-14) lose
  electrons producing cations (positive ions)
• the term oxidized (O.I.L Oxidized Is Losing) is
  used to say it lost an electron
• example- Ca becomes Ca2

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• anions
• atoms of nonmetallic elements (groups 15, 16, 17)
  gain electrons producing anions (negative ions)
• the term reduced (R.I.G.) Reduction Is Gaining)
  is used to say it gained an electron
• example- Cl becomes Cl1-

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Ne
N
F
O
Na
Mg
N3-
Na
O2-
Mg2
F1-
Cations
Anions
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1
2
3-
3
4/-
2-
1-
0


  ...etc.   ...etc.
As it turns out, atoms bond together for a very
simple reason atoms that have full valence
shells are more stable than those that dont.
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• some transitional metals can often form more than
  one cation and therefore charges may vary
• some orbitals get filled but might not get a
  noble gas electron configuration
• iron can be Fe2 or Fe3 (you dont have to
  memorize this)
• these always have the same charge
• Sc3, Zn2, Cd2, Ag1 (you do have to memorize
  these)

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Formation of Ionic Compounds

• usually composed oppositely charged metallic
  cations and nonmetallic anions
• because of the electrostatic attraction between
  oppositely charged particles
• electro- electricity/electrons
• static- non-moving (vs. current which is moving
  charges)

- anions
cations
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• forms a compound with overall zero charge
• ( and -) need to cancel out
• referred to as formula units, not a molecule,
  that is a term used only for covalently bonds
  which is something different

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• ions must have a difference in electronegativity
  of 1.7 or greater to form an ionic bond

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electronegativty difference
probable type of bond
0.0
covalent, nonpolar
covalent, slightly polar
0.1 1.0
covalent, very polar
1.1 1.7
ionic
gt1.7
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Na gives Cl one electron and now both atoms
have a full valence shell (electron configuration
of a noble gas)
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3)
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Chemical Formula

• shows the kinds and numbers of atoms in the
  lowest whole-number ratio of ions in the ionic
  compound
• Na 1 Cl 1- ? NaCl
• Ca 2 Cl 1- ? CaCl2
• Mg 2 O 2- ? MgO

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• Mg and N?
• Mg2, N3-
• it takes two nitrogens to combine with three
  magnesiums
• Mg3N2
• magnesium nitride

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Na 1 F 1- ? NaF
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Properties of Ionic Compounds

• high melting and boiling points
• takes a lot of energy to break apart the
  electrostatic forces between cations and anions
• crystalline structure
• repeating arrays of cations and ions
• an ionic lattice

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• volatility- how easily a substance turns into a
  gas
• very low as electrostatic forces between cations
  and anions is very strong
• electrical conductivity
• can conduct electric currents when melted or
  dissolved in water because cations and anions are
  free moving instead in a lattice
• solubility
• will dissolve in other polar solvents such as
  water

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Naming Ions and Writing Ionic Compounds
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Monoatomic ions
Naming Ions

• cations lose valence electrons and therefore are
  positively charged
• transition metals form more than one cation with
  different ionic charges
• charge is determined from the of electrons lost
• Fe2 lost two electrons (the 2 in the 4s)
• Fe3 lost three electrons (the 2 in the 4s and 1
  in the 3d)
• naming
• Stock system
• a Roman numeral is used to show the charge of the
  transition metal
• Fe2 is iron(II) and Fe3 is iron(III)

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• anions gain valence electrons and therefore are
  negatively charged
• change ending to ide for the name

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Polyatomic ions (look at list)

• composed of more than one atom that form a single
  unit/ion with a charge
• most end with -ite or ate
• the ite ending indicates one less oxygen than
  the ate ending
• ionic charge is the same for both

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Memorize these! Memorize these!
NO31- nitrate
NO21- nitrite
OH1- hydroxide
ClO21- chlorite
ClO31- chlorate
HCO31- hydrogencarbonate (bicarbonate)
SO42- sulfate
SO32- sulfite
CO3 2- carbonate
PO43- phosphate
NH41 ammonium
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Naming ionic compounds

• Binary Compounds
• cation is written first, followed by the anion
  with and ide ending
• Cs2O ? cesium oxide
• SrF2 ? strontium fluoride
• CuO ? copper(II) oxide
• oxygen is always 2- and therefore copper will be
  2
• Cu2O ? copper(I) oxide
• oxygen is 2- and therefore needed two copper
  atoms with 1 charge

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• SnF2 ? ?
• fluorine is always 1- and therefore tin will be
  2
• tin(II) fluoride
• SnS2 ? ?
• sulfur is always 2- and therefore tin will be 4
• tin(IV) sulfide

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Writing formulas for ionic compounds

• write symbol of cation and then anion
• add subscripts to balance the charges
• calcium bromide
• Ca2 and Br1- is CaBr2
• potassium sulfide
• K1 and S2- is K2S
• iron(III) oxide
• Fe3 and O2- is Fe2O3

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crisscross method

• the ionic charge number of each ion is crossed
  over and becomes the subscript for the other ion

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• Compounds with polyatomic ions
• do same as binary compounds
• use the name of the polyatomic ion with the mono
  atomic ion
• calcium nitrate ? ?
• Ca is 2 and nitrate is 1-
• Ca(NO3)2
• Li2CO3 ? ?
• lithium carbonate

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Names to Formulas

• aluminum chloride

1. Write symbols of elements
2. Determine number of ions
(Al )x(Cl-1)y
3
If there is no Roman Numeral, you must know the
oxidation number of the positive ion.
For aluminum, a 1 is multiplied times the 3 to
give a 3 charge
What is the Lowest Common Multiple LCM of 3 and
1. Do not worry about the sign(/-)
What is the Lowest Common Multiple LCM of 3 and
1. Do not worry about the sign(/-)
x(3) y(-1) 0
For chloride, a 3 is multiplied times the -1 to
give a -3 charge
If there is no Roman Numeral, you must know the
oxidation number of the positive ion.
Remember all compounds are neutral, thus the
total positive charge must equal the total
negative charge
This formula says that the 3 charge of one
Al atom will cancel the-3 charge from 3 Cl atoms
1(3) 3(-1) 0
Cl
Al
3
1
If there is only one atom the 1 is not shown
Final Formula
Next
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Formula to Name

• Fe(NO3)3

Choose the correct name for the compound
1. Iron trinitrate
No, you do not use prefixes
2. iron(I) nitrate
No, you have the wrong oxidation number
3. iron(III) nitrite
No, you need to review polyatomic ions
4. iron(III) nitrate
Very good, click arrow to continue
5. none of the above
No, there is a correct answer
Polyatomic Ions
next problem
Periodic Chart
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Name to Formula

• sodium chlorite

Choose the correct formula for the compound
1. NaCl
No, you need to review prefixes
2. NaClO
No, you need to review prefixes
3. NaClO2
Very good, click arrow to continue
No, you have several errors
4. Na(ClO)2
No, there is a correct answer
5. none of the above
next problem
Prefixes
Periodic Chart