The Nonmetal-Nonmetal
vs Metal – Nonmetal Bond
Lewis Dot Structures
• A famous chemist named Lewis invented a
symbol to show valence electrons. He used
a dot next to the symbol to represent each
valence electron. The dots are spread
around the 4 sides.
• Each pair of dots
Represents a bond.
Covalent Bonds
•What is a Covalent Bond?
•?
- A covalent bond is a chemical
bond resulting from SHARING
of electrons between 2
nonmetals.
Covalent Bonds can have multiple bonds, so you should be
familiar with the following…
Single Covalent Bondchemical bond resulting
from sharing of an electron
pair between two atoms. H2O
Double Covalent Bondchemical bond resulting
from sharing of two electron
pairs between two atoms.
CO2
Triple Covalent Bondchemical bond resulting
from sharing of three
electron pairs between two
atoms. N2
Types of Covalent Bonds
• Two types of colvalent bonds: nonpolar and polar
• Recall electronegativity (desire for electrons) -see
shaded table on ole yeller
• The electronegativity difference between the two
atoms determines whether it is a nonpolar or
polar bond.
Electronegativity difference:
0
.4
Nonpolar Polar
2.0
Ionic
Polar Bonds
A nonpolar bond tends to share electrons equally
A polar bond means there is a dipole or one pole
(end) with a positive charge and one pole (end)
with a negative charge, therefore they tend to
stick together better since their opposite charges
attract. (=)(-)
Very strong polar bonds are
ionic bonds like NaCl
Covalent Bonds Do NOT have ions
or need to Balance Charges
• They use prefixes to
show the number of
atoms:
• Mono• Di• Tri• Tetra-
• Examples:
• H2O =
dihydrogen
monoxide
• CO2 = carbon
dioxide
• dinitrogen tetraoxide
= N2O4
• Phosphorus
trichloride = PCl3
Pop Quiz: Covalent Bonds:
HOT or NOT?
HOT, for sure!
If Miley says it’s hot, it’s HOT!
When a metal and nonmetal come
together, a pair of electrons acts as a
bond and they each become ions.
Ionic Bonding Rules:
• Metal first, nonmetal second
• Nonmetal ion becomes ‘ide’
• Metal is positive, nonmetal is
negative
• Charges must balance to zero
• Formula uses a subscript to
balance charges
• Example: MgCl2 ; Na2O; NaCl
The sodium atom and chloride atom
bond together as ions and form a new
compound.
This is called an ionic bond.
Practice:
Sodium and
fluorine
Barium and
iodine
lithium and
phosphorus
Aluminum and
oxygen
Beryllium and
oxygen
Calcium and
nitrogen
Answers:
Sodium and
Barium and
fluorine
iodine
sodium fluoride barium iodide
NaF
BaI2
lithium and
phosphorus
lithium
phosphide
Li3P
Aluminum and Beryllium and Calcium and
oxygen
sulfur
nitrogen
aluminum
beryllium
calcium nitride
oxide
sulfide
Ca3N2
Al2O3
BeS
Solutions
• When ionic compounds are put in water,
they dissolve into ions:
Polyatomic ions: are groups of
atoms bonded together with a
charge hence the name “poly”
“atomic” “ions”.
•
•
•
•
•
Examples:
OH-1 = hydroxide
NO3-1 = nitrate
PO4-3 = phosphate
SO4-2 = sulfate
Practice: Use polyatomic ions just
like any other ion; But when you
have more than one , use
parentheses.
• barium hydroxide=
(Notice parentheses show multiple
ions.)
barium hydroxide= Ba OH
+2 -1
Ba(OH)2
+2 -1(2) = 0
• strontium nitrate =
• strontium nitrate = Sr NO3
+2 -1
strontium nitrate = Sr(NO3)2
+2 + -1(2)
• lithium phosphate
• lithium phosphate = Li PO4
+1 -3
lithium phosphate Li3PO4
+1(3) + -3 = 0
potassium sulfate
• potassium sulfate = K SO4
+1
-2
potassium sulfate = K2SO4
+1(2) + -2 = 0
Transition metals: Metals that
have more than one possible
charge:
•
•
•
•
Cobalt: Co+2, Co+3
Copper: Cu+, Cu+2
Iron: Fe+2, Fe+3
Lead: Pb+2, Pb+4
• When writing the names,
always use roman numerals to
show the charge.
Examples:
•
•
•
•
Cobalt (II) Co+2, Cobalt (III) Co+3
Copper(I), Cu+, or Copper (II), Cu+2
Iron(II) Fe+2, or iron (III), Fe+3
Lead(II), Pb+2, or lead (IV), Pb+4
• Each different charged ion
behaves completely different
than the other! The charges
matter!
Practice!
Lead (IV) hydroxide
• Lead(IV) hydroxide = Pb(OH)4
• Copper (II) nitrate
• Copper(II) nitrate = Cu(NO3)2
+2 -1
• CoPO4
• CoPO4 = Cobalt (III) phosphate
+3 -3
• Fe2(SO4)3
+3 -2
Iron (III) sulfate Fe2(SO4)3
Hydrates
Some ionic compounds absorb water molecules
into their structures. These are called hydrates.
NaCl•2H2O is the symbol for sodium chloride
dihydrate. Notice the prefix di- means 2 water
molecules.
Name these hydrates: MgSO4•5H2O
CuCl2•4H2O
Finding Percentage of Water
in a Hydrate
You can find the percentage of water in a hydrate
by dividing the mass of the water by the total
mass times 100.
Lets take NaCl•2H2O
Using the periodic table, the mass of Na=23,
Cl=35.5, H2O = 18. Total mass with 2 H20 is 94.4
Water mass (36)/ Total (94.4) x 100
= 38 % water
What are the differences between
ionic bonding and covalent
bonding? List them below:
Differences:
•
•
•
•
Ionic
Metal , nonmetal-ide
Balance charges using
subscripts
Polyatomic ions use
parentheses in
multiples
Transition metals use
roman numerals to
show charge
Differences:
•
•
•
•
•
Covalent
Two nonmetals
Nonmetal, nonmetalide
No ions- they share eUse prefixes
Don’t need to balance
Differences:
•
•
•
•
Ionic
Metal , nonmetal-ide
Balance charges
using subscripts
Polyatomic ions use
parentheses in
multiples
Transition metals use
roman numerals to
show charge
•
•
•
•
•
Covalent
Two nonmetals
Nonmetal, nonmetalide
No ions- they share eUse prefixes
Don’t need to
balance
Ionic bonds: HOT or
NOT?
Definitely HOT Baby!