C8_U4_L3_BinaryIonicCompounds.ppt.........

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1. Bellwork
1.Name the following
compounds
a)Na
3N
b)KBr
c)MgS
2.Give the formula for a
compound of:
a)Cesium and Phosphorus
b)Strontium and chlorine
c)Potassium and selenium
Homework
WS 4.3

2. Ionic Compounds
Attraction between + ions and - ions
Electrons are transferred from to the more
electronegative element (nonmetals)

electron transfer
metal

nonmetal
Important: Electrons lost = Electrons gained

3. Formulas of Ionic Compounds
Formulas of ionic compounds are
determined from the charges on the ions.


atoms ions
Na + F  Na
+
+

F
-
 NaF
sodium + fluorine react to form sodium fluoride.
1+ + 1-  0 (neutral)

4. •Rule of zero charge: In an ionic compound, the
positive charges on the metal cations and the
negative charges on the nonmetal anions MUST
sum to 0.
•Subscripts are used if more than one atom is
needed to cancel the charges.
•Ex. Lithium oxide: Li
+
and O
2-
 Li
2
O
•Two lithium atoms are needed per one oxygen
atom in order to follow the rule of zero charge.
Rule of Zero Charge

5. Mg
2+
+ Cl
–
+ Cl
–
produces MgCl
2
with zero charge.

6. Writing Formulas of Ionic
Compounds
Ex. Write the formula for the ionic compound that will form
between Ba
2+
and Cl

.
Steps:
1. Write the cation first and then the anions
to balance the charge on the cation.
Ba
2+
+ Cl

+ Cl

2. Write the number of ions needed (to
balance the charges) as subscripts.

BaCl
2

7. Practice: Write the correct formula for
the compounds containing the
following atoms:
1.Na & S
2.Al & Cl
3.Mg & N
4.K & Se
5.Ba & I
1.Na
2S
2.AlCl
3
3.Mg
3
N
2
4.K
2
Se
5.BaI
2

8. Naming Binary Ionic
Compounds
Ex. Write the name of the chemical with formula NaBr.
Steps:
1.Write the name of the metal.
2.Write the name of the non-metal, but change the
ending to –ide.
Solution: Sodium bromide

9. Practice: Naming Binary Ionic
Compounds
LiI Ca
3
N
2
CaBr
2
Al
2
O
3
Ag
2
O BaCl
2
BeS K
3P
lithium iodide
calcium bromide
silver oxide
beryllium sulfide
calcium nitride
aluminum oxide
barium chloride
potassium phosphide

10. Lattice Energy (LE)
•the energy required to separate 1 mol of an ionic solid into
gaseous ions (completely break apart the bond).
•Greater lattice energy = high melting point for ionic compounds
There are two factors which govern the magnitude of lattice
energy:
i) Charge on the ions (greater magnitude)
ii) Radius of the ions (smaller radius)
•The higher the charge on the ion, the higher the lattice energy
(Coulomb’s Law). MgO would have a greater lattice energy/higher
melting point than NaCl. This is because the charge on the ions is
greater in MgO
•Secondarily, a smaller atomic radius leads to greater lattice energy
as well. LiF would have greater lattice energy than NaCl due to the
small ionic radii of Li
+
and F
-

11. Trends in lattice energy