4 5 covalent compounds
TRANSCRIPT
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Chapter 4 Compounds and Their Bonds
4.5Covalent Compounds
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
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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).
Covalent Bonds
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Hydrogen Molecule
A hydrogen molecule
• is stable with two 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 one electron.
• attains an octet.
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Carbon forms 4 covalent bonds
In a CH4, methane, molecule
• a C atom shares 4 electrons to attain an octet.
• each H shares 1 electron to become stable like helium.
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Multiple Bonds
In 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.
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Naming Covalent Compounds
To name covalent compounds• STEP 1: Name the first
nonmetal as an element. • STEP 2: Name the second
nonmetal with an ide ending.
• STEP 3: Use prefixes to indicate the number of atoms (subscript) of each element.
Table4.12
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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.
Naming Covalent Compounds
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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
Naming Covalent Compounds
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Formulas and Names of Some Covalent Compounds
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
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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
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Select the correct name for each compound.
A. SiCl4 3) silicon tetrachloride
B. P2O5 3) diphosphorus pentoxide
C. Cl2O7 1) dichlorine heptoxide
Solution
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Write the name of each covalent compound.
CO _____________________
CO2 _____________________
PCl3 _____________________
CCl4 _____________________
N2O _____________________
Learning Check
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Write the name of each covalent compound.
CO carbon monoxide
CO2 carbon dioxide
PCl3 phosphorus trichloride
CCl4 carbon tetrachloride
N2O dinitrogen monoxide
Solution
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The prefixes in the name are used to write the formula.
STEP 1: Write the symbols in the order of the elements in
the name.
STEP 2: Write any prefixes as subscripts.
Example: 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
Guide to Writing Formulas
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Write the correct formula for each of the following.
A. phosphorus pentachloride
B. dinitrogen trioxide
C. sulfur hexafluoride
Learning Check
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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
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Learning Check
Identify each compound as ionic or covalent and give itscorrect name.
A. SO3
B. BaCl2C. (NH4)3PO4
D. Cu2CO3
E. N2O4
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Solution
Identify each compound as ionic or covalent and give itscorrect name.
A. SO3 covalent – sulfur trioxide
B. BaCl2 ionic – barium chloride
C. (NH4)3PO3 ionic – ammonium phosphite
D. Cu2CO3 ionic – copper(I) carbonate
E. N2O4 covalent – dinitrogen tetroxide
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Learning Check
Name the following compounds.
A. Ca3(PO4)2
B. FeBr3
C. SCl2
D. Cl2O
E. N2
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Solution
Name the following compounds.
A. Ca3(PO4)2 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 monoxide
E. N2 covalent 2N(element) nitrogen
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Learning Check
Write the formulas for the following.
A. calcium nitrate
B. boron trifluoride
C. aluminum carbonate
D. dinitrogen tetroxide
E. copper(I) phosphate
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Solution
Write the formulas for the following.
A. calcium nitrate Ca2+, NO3−
Ca(NO3)2
B. boron trifluoride 1 B, 3 F BF3
C. aluminum carbonate Al3+, CO32− Al2(CO3) 3
D. dinitrogen tetroxide 2 N, 4 O N2O4
E. copper(I) phosphate Cu+, PO43−
Cu3PO4
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Predicting Compounds using Lewis Dot Structures
Going back to the idea of Lewis dot configuration as a good way to keep track of valence electrons for predicting structure of ionic/covalent compounds.
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Ionic Compounds
Magnesium Iodide using the crossover method to determine the molecular formula and draw the structure using Lewis dot valence electrons.
Step 1: Forming the magnesium cation:
Mg2+Mg + 2e-
Step 2: Forming the iodide anion:
I + 1e- I
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Step 3: Putting the ions together
We need 2 iodide anions to balance the +2 charge on the magnesium, as indicated by the formula MgI2
IMg2+I
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Covalent Compounds
Covalent compounds between oxygen and hydrogen
Step 1: Determine how many bonds are formed by oxygen
Step 2: Determine how many hydrogen atoms are in the chemical formula (hydrogen forms a single bond)
Step 3: Draw the structure
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Draw the structure for H2O
O6 valence e- 2 max bonds
O H
H
O H2
6 valence e-
and
1 valence e-H2O
H1 valence e- 1 bond each
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Covalent Compounds
Covalent compounds between carbon and hydrogen
Step 1: Determine how many bonds are formed by carbon
Step 2: Determine how many hydrogen atoms are in the chemical formula (hydrogen forms a single bond)
Step 3: Draw the structure
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Draw the structure for CH4
H1 valence e- 1 bond each
4 valence e- 4 max bondsC
H4
4 valence e-
and
1 valence e-
CH4
C H
H
C
H
H