1
Chapter 6 Inorganic and Organic Compounds: Names and Formulas
6.5
Covalent Compounds and Their Names
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2
Forming a H2 Molecule
Basic Chemistry Copyright © 2011 Pearson Education, Inc.
A covalent bond forms as H atoms move close together to share electrons.
3
H2, A Covalent Molecule
In a hydrogen (H2) molecule,
• two hydrogen atoms share electrons to form a covalent single bond
• each H atom acquires two (2) electrons
• each H becomes stable like helium (He)
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4
Diatomic Elements
• These elements share electrons to form diatomic, covalent molecules.
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5
What is the name of each of the following diatomic molecules?
H2 ______________________
N2 _______________
Cl2 _______________
O2 _______________
I2 _______________
Learning Check
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6
What are the names of each of the following diatomic molecules?
H2 hydrogen
N2 nitrogen
Cl2 chlorine
O2 oxygen
I2 iodine
Solution
Basic Chemistry Copyright © 2011 Pearson Education, Inc.
7
Electron-Dot Formulas
Electron-dot formulas show
• the order of bonded atoms in a covalent compound
• the bonding pairs of electrons between atoms
• the unshared (lone) valence electrons
• a central atom with an octet
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8
Electron-Dot Formulas and Models of Some Covalent Compounds
Basic Chemistry Copyright © 2011 Pearson Education, Inc.
9
Names of Covalent Compounds
Prefixes are used• in the names of covalent compounds• because two nonmetals can form two or
more different compounds
Examples of compounds of N and O:
NO nitrogen oxide
NO2 nitrogen dioxide
N2O dinitrogen oxide
N2O4 dinitrogen tetroxide
N2O5 dinitrogen pentoxide
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11
To name the covalent compound SO3,
STEP 1 Name the first nonmetal by its element name. The element S is sulfur.
STEP 2 Name the second nonmetal by using the first syllable of its element name followed by ide. O is named oxide.
STEP 3 Add prefixes to indicate the number of atoms (subscripts). The subscript 3 of O is shown as the prefix tri.
SO3 → sulfur trioxide The subscript 1(for S) or mono is
understood.
Naming Covalent Compounds
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12
What is the name of P4S3?
STEP 1 Name the first nonmetal by its element name. P is named phosphorus.
STEP 2 Name the second nonmetal by using the first syllable of its element name followed by ide. S is named sulfide.
STEP 3 Add prefixes to indicate the number of atoms (subscripts). The subscript 4 of P is written as tetra. The subscript 3 of O is written as tri.
P4S3 → tetraphosphorus trisulfide
Naming Covalent Compounds
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13
Formulas and Names of Some Covalent Compounds
Basic Chemistry Copyright © 2011 Pearson Education, Inc.
14
Select the correct name for each compound.
A. SiCl4 1) silicon chloride
2) tetrasilicon chloride3) silicon tetrachloride
B. P2O5 1) phosphorus oxide
2) phosphorus pentoxide3) diphosphorus pentoxide
C. Cl2O7 1) dichlorine heptoxide
2) dichlorine oxide3) chlorine heptoxide
Learning Check
Basic Chemistry Copyright © 2011 Pearson Education, Inc.
15
Select the correct name for each compound.
A. SiCl4 3) silicon tetrachloride
B. P2O5 3) diphosphorus pentoxide
C. Cl2O7 1) dichlorine heptoxide
Solution
Basic Chemistry Copyright © 2011 Pearson Education, Inc.
16
Write the name of each covalent compound:
CO _____________________
CO2 _____________________
PCl3 _____________________
CCl4 _____________________
N2O _____________________
Learning Check
Basic Chemistry Copyright © 2011 Pearson Education, Inc.
17
Write the name of each covalent compound:
CO carbon monoxide
CO2 carbon dioxide
PCl3 phosphorus trichloride
CCl4 carbon tetrachloride
N2O dinitrogen oxide
Solution
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18
Example: Write the formula for carbon disulfide.
STEP 1 Write the symbols in the order of the elements in the name. C S
STEP 2 Write any prefixes as subscripts. No prefix for carbon means one(1) C. The prefix di for sulfur means two(2) S.
formula: CS2
Guide to Writing Formulas
Basic Chemistry Copyright © 2011 Pearson Education, Inc.
19
Write the correct formula for each of the following:
A. phosphorus pentachloride
B. dinitrogen trioxide
C. sulfur hexafluoride
Learning Check
Basic Chemistry Copyright © 2011 Pearson Education, Inc.
20
Write the correct formula for each of the following:
A. phosphorus pentachloride
1 P penta = 5 Cl PCl5
B. dinitrogen trioxide
di = 2 N tri = 3 O N2O3
C. sulfur hexafluoride
1 S hexa = 6 F SF6
Solution
Basic Chemistry Copyright © 2011 Pearson Education, Inc.
21
Learning Check
Identify each compound as ionic or covalent and
give its correct name.
A. SO3
B. MnCl2
C. (NH4)3PO4
D. Cu2CO3
E. N2O4
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22
SolutionIdentify each compound as ionic or covalent and
give its correct name.
A. SO3 covalent; sulfur trioxide
B. MnCl2 ionic; manganese(II) chloride
C. (NH4)3PO3 ionic; ammonium phosphite
D. Cu2CO3 ionic; copper(I) carbonate
E. N2O4 covalent; dinitrogen tetroxide
Basic Chemistry Copyright © 2011 Pearson Education, Inc.
23
Learning Check
Identify each compound as ionic or covalent and
give its correct name.
A. Ca3(PO4)2
B. FeBr3
C. SCl2
D. Cl2O
Basic Chemistry Copyright © 2011 Pearson Education, Inc.