Transcript 4.5 Covalent Compounds

Chapter 4
Compounds and Their Bonds
4.5
Covalent Compounds
Copyright © 2009 by Pearson Education, Inc.
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Covalent Bonds
Covalent bonds form
• when atoms share electrons to complete octets.
• between two nonmetal atoms.
• between nonmetal atoms from Groups 4A (14),
5A (15), 6A (16), and 7A (17).
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Hydrogen Molecule
A hydrogen molecule
• is stable with 2 electrons (helium).
• has a shared pair of electrons.
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Forming Octets in Molecules
In a fluorine, F2,, molecule, each F atom
• shares 1 electron.
• attains an octet.
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Carbon Forms 4 Covalent Bonds
In a CH4 (methane) molecule,
• 1 C atom shares electrons
with 4 H atoms to attain an
octet.
• each H atom shares 1
electron to become stable,
like helium.
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Multiple Bonds
In a nitrogen molecule, N2,
•
•
•
•
each N atom shares 3 electrons.
each N attains an octet.
the bond is a multiple bond called a triple bond.
the name is the same as the element.
Copyright © 2009 by Pearson Education, Inc.
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Naming Covalent Compounds
In the names of covalent compounds, prefixes are
used to indicate the number of atoms (subscript) of
each element. (mono is usually omitted)
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Guide to Naming Covalent
Compounds
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Naming Covalent Compounds
What is the name of SO3?
1. The first nonmetal is S sulfur.
2. The second nonmetal is O, named oxide.
3. The subscript 3 of O is shown as the prefix tri.
SO3 -> sulfur trioxide
The subscript 1 (for S) or mono is understood.
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Naming Covalent Compounds
Name P4S3.
1. The first nonmetal, P, is phosphorus.
2. The second nonmetal, S, is sulfide.
3. The subscript 4 of P is shown as tetra.
The subscript 3 of O is shown as tri.
P4S3 -> tetraphosphorus trisulfide
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Formulas and Names of Some
Covalent Compounds
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Learning Check
Select the correct name for each compound.
A.
SiCl4
1) silicon chloride
2) tetrasilicon chloride
3) silicon tetrachloride
B.
P2O5
1) phosphorus oxide
2) phosphorus pentoxide
3) diphosphorus pentoxide
C.
Cl2O7
1) dichlorine heptoxide
2) dichlorine oxide
3) chlorine heptoxide
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Solution
Select the correct name for each compound.
A.
B.
C.
SiCl4
P2O5
Cl2O7
3) silicon tetrachloride
3) diphosphorus pentoxide
1) dichlorine heptoxide
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Learning Check
Write the name of each covalent compound.
CO
CO2
PCl3
CCl4
N2O
_____________________
_____________________
_____________________
_____________________
_____________________
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Solution
Write the name of each covalent compound.
CO
CO2
PCl3
CCl4
N2O
carbon monoxide
carbon dioxide
phosphorus trichloride
carbon tetrachloride
dinitrogen oxide
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Guide to Writing Formulas for
Covalent Compounds
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Example: Writing Formulas for
Covalent Compounds
Write the formula for carbon disulfide.
STEP 1:
Elements are C and S
STEP 2:
No prefix for carbon means 1 C
Prefix di = 2
Formula: CS2
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Learning Check
Write the correct formula for each of the following:
A. phosphorus pentachloride
B. dinitrogen trioxide
C. sulfur hexafluoride
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Solution
Write the correct formula for each of the following:
A. phosphorus pentachloride
1P
penta = 5 Cl
PCl5
B. dinitrogen trioxide
di = 2 N tri = 3 O
N2O3
C. sulfur hexafluoride
1S
hexa = 6 F
SF6
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Learning Check
Identify each compound as ionic or covalent, and give its
correct name.
A.
B.
C.
D.
E.
SO3
BaCl2
(NH4)3PO3
Cu2CO3
N 2O 4
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Study Tip: Ionic or Covalent
A compound is
• ionic if the first element in the formula
or the name is a metal or the polyatomic ion NH4+ .
K2O K is a metal; compound is ionic;
potassium oxide
• covalent if the first element in the formula or the name
is a nonmetal.
N2O N is a nonmetal; compound is covalent;
dinitrogen oxide
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Solution
Identify each compound as ionic or covalent and give its
correct name.
A.
B.
C.
D.
E.
SO3
BaCl2
(NH4)3PO3
Cu2CO3
N 2O 4
covalent – sulfur trioxide
ionic – barium chloride
ionic – ammonium phosphite
ionic – copper(I) carbonate
covalent – dinitrogen tetroxide
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Learning Check
Identify each compound as ionic or covalent and give its
correct name.
A. Ca3(PO4)2
B. FeBr3
C. SCl2
D. Cl2O
E. N2
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Solution
Identify each compound as ionic or covalent and give its
correct name.
A. Ca3(PO4) ionic
Ca2+ PO43−
calcium phosphate
B. FeBr3
ionic
Fe3+ Br −
iron(III) bromide
C. SCl2
covalent
1S 2 Cl
sulfur dichloride
D. Cl2O
covalent
2 Cl 1 O
dichlorine oxide
E. N2
covalent
element
nitrogen
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Learning Check
Determine if each is ionic (I) or covalent (C ), and write
the formula.
A. calcium nitrate
B. boron trifluoride
C. aluminum carbonate
D. dinitrogen tetroxide
E. copper(I) phosphate
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Solution
Determine if each is ionic (I) or covalent (C ), and write
the formula.
A. calcium nitrate
(I)
Ca2+, NO3−
Ca(NO3)2
B. boron trifluoride
(C)
1 B, 3 F
BF3
C. aluminum carbonate (I) Al3+, CO32−
Al2(CO3) 3
D. dinitrogen tetroxide (C) 2 N, 4 O
N2O4
E. copper(I) phosphate (I) Cu+, PO43−
Cu3PO4
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