1. IONIC BONDS
Chapter 4 Section 1

2. Octet Rule: Atoms “want” 8 valence electrons to be stable
Review
Octet Rule: Atoms “want” 8 valence electrons to be stable
some atoms have “extra” valence electrons
some atoms “need” more valence electrons

3. Review
Shortcut to know the number of valence electrons...1’s digit of group number
Group 1  1 valence electron
Group 2  2 valence electrons
Group 13  3 valence electrons
Group 14  4 valence electrons
Group 15  5 valence electrons
Group 16  6 valence electrons
Group 17  7 valence electrons
Group 18  8 valence electrons

4. Ion – atom or group of atoms that has become electrically charged
Ions
Ion – atom or group of atoms that has become electrically charged
Atoms become ions by…
losing an electron
more protons than electrons  becomes positive
gaining an electron
more electrons than protons  becomes negative

5. Charges
The charge of an ion depends on how many electrons it gains or loses.
Ex) Chlorine (7 valence electrons) will gain one electron to have a full outer shell. This means it has 18 negative charges (electrons) to 17 positive charges (protons), giving it an overall charge of -1.
Try:
Sulfur
Potassium
S2-
K1+

6. Charges
You can predict an ion’s charge based on the element’s location in the periodic table:
Group 17 elements will gain 1 electron  charge = -1
Group 16 elements will gain 2 electrons  charge = -2
Group 15 elements will gain 3 electrons  charge = -3
Group 1 elements will lose 1 electron  charge = +1
Group 2 elements will lose 2 electrons  charge = +2
Group 13 elements will lose 3 electrons  charge = +3
Group 14 can be -4 or +4 (gain or lose 4 electrons)

7. Ionic Bonds formed by ions who’s opposing charges attract.
Example: Sodium Chloride (NaCl) “Table Salt”
Sodium (Na) has an extra electron (1 valence electron)
Chlorine (Cl) needs one more (7 valence electrons)
If Na transfers its electron to Cl…
both become more stable as ions.
Chlorine  negative ion (Cl-)
Sodium  positive ion (Na+)
opposite charges attract and bond the atoms like magnets.

8. Neutral Compounds – Ionic compounds are electrically neutral.
IONIC BONDS
Neutral Compounds – Ionic compounds are electrically neutral.
Ions bond so that the charges balance.
ex) It takes 1 sodium ion (Na+) to balance out 1 chloride ion (Cl-)  NaCl (sodium chloride)
ex) It takes 1 calcium ion (Ca2+) to balance out 2 chloride ions (Cl-)  CaCl2 (calcium chloride)

9. Polyatomic Ions – ions made of more than one atom
a group of atoms that act as one ion
Example: Carbonate (CO32-)
One Carbon ion (+4)
Three Oxygen ions (-2) + (-2) + (-2) = (-6)
Overall charge (+4) + (-6) = (-2)
Common polyatomic ions on p.115

10. Naming Compounds usually the name of a metal (ex: sodium)
the name of the positive ion comes first
usually the name of a metal (ex: sodium)
sometimes a positive polyatomic ion (ex: ammonium)
the name of the negative ion comes second
if an element, the end changes to “-ide” (ex: oxide)
if polyatomic, the name is unchanged (ex: carbonate)
Al2S3
Na2CO3
aluminum sulfide
sodium carbonate

11. Try These (use p.115 for help)
Name the following:
NaCl
CaCl2
LiNO3
MgCl2
NH4F
sodium chloride
calcium chloride
lithium nitrate
magnesium chloride
ammonium fluoride

12. Try These (use p.115 for help)
Give the correct formula: Remember to form a neutral compound!
potassium bicarbonate
sodium sulfate
calcium fluoride
lithium sulfide
aluminum oxide
KHCO3
Na2SO4
CaF2
Li2S
Al2O3

13. Properties of Ionic Compounds
Crystal Shape
Atoms form organized, alternating, 3-D pattern
High Melting Point
Solids at room temp.
Electrical Conductivity
conduct electricity well in solution (or when melted)