Variable Charge
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Transcript of Variable Charge
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© 2013 Pearson Education, Inc. Chapter 5, Section 1 1
Metals with Variable Charge
Most transition metals (3-12) and Group 4A (14) metals form 2 or more positive ions, except Zn2+, Ag+, and Cd2+, which form only one ion.
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Metals with Variable Charge
The names of transition metals with two or more
positive ions (cations) use a Roman numeral after the
name of the metal to identify the ion charge.
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Naming Ionic Compounds with Variable Charge Metals
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Naming FeCl2
Step 1 Determine the charge of the cation from the anion. Analyze the Problem.
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Naming FeCl2
Step 2 Name the cation by its element name and use a Roman numeral in parentheses for the charge.
Fe2+ = iron(II) Step 3 Name the anion by using the first syllable of its element name followed by ide . Cl− = chloride Step 4 Write the name for the cation first and the name for the anion second.
iron(II) chloride
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© 2013 Pearson Education, Inc. Chapter 5, Section 1 6
Examples of Names of Compounds with Variable Charge Metals
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Writing Formulas for Ionic Compounds
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Writing the Formula for Iron(III) Oxide
Metal Nonmetal
Ion Iron(III) oxide
Group Transition 6A (16)
Symbol Fe3+ O2–
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Learning Check
Write the correct name for CuO.
Write the correct formula for copper(I) nitride.
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A polyatomic ion
is a group of atoms.
has an overall ionic charge.
Examples:
NH4+ ammonium OH− hydroxide
SO42−
sulfate CO32− carbonate
PO43− phosphate
Polyatomic Ions
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© 2013 Pearson Education, Inc. Chapter 5, Section 1 11
Names and Formulas of Common Polyatomic Ions
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Compounds Containing Polyatomic Ions
Polyatomic ions
must be associated with an ion of opposite charge.
form ionic bonds with ions of opposite charge to achieve charge balance.
Example:
Ca2+ NO3−
calcium nitrate ion
charge balance:
Ca(NO3)2
calcium nitrate
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Step 1 Identify the cation and polyatomic ion (anion).
Cation: K+ Anion: SO42−
Step 2 Name the cation, using a Roman numeral if needed.
K+ = potassium ion
Step 3 Name the polyatomic ion.
SO42− = sulfate ion
Step 4 Write the name or the compound, cation first and the polyatomic ion second.
K2SO4 = potassium sulfate
Name K2SO4
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Learning Check
Name each of the following compounds.
1. Cu(ClO3)2
2. PbCO3
3. Ba3(PO3)2
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Solution
Step 1 Identify the cation and polyatomic ion (anion). cation polyatomic ion 1. Cu(ClO3)2 Cu2+ ClO3
−
2. PbCO3 Pb2+ CO32−
3. Ba3(PO3)2 Ba2+ PO33−
Step 2 Name the cation using a Roman numeral, if necessary. cation name 1. Cu(ClO3)2 copper(II)
2. PbCO3 lead(II) 3. Ba3(PO3)2 barium
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Solution
Step 3 Name the polyatomic ion. polyatomic ion 1. Cu(ClO3)2 chlorate
2. PbCO3 carbonate 3. Ba3(PO4)2 phosphate
Step 4 Write the name or the compound, cation first
and the polyatomic ion second. compound name 1. Cu(ClO3)2 copper(II) chlorate
2. PbCO3 lead(II) carbonate 3. Ba3(PO3)2 barium phosphite
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Write the Formula for Aluminium Hydroxide
Step 1 Identify the cation and polyatomic ion (anion). Al3+ and OH−
Step 2 Balance the charges. Step 3 Write the formula, cation first, using the subscripts from charge balance. Al(OH)3
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Break Time!!
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Covalence - Formation of H2
In the simplest covalent molecule, H2 , the H atoms
increase attraction as they move closer.
share electrons to achieve a stable configuration.
form a covalent bond.
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© 2013 Pearson Education, Inc. Chapter 5, Section 1 20
Electron-Dot Formulas of Covalent Molecules
In a fluorine (F2) molecule, the F atoms
share one of their valence electrons.
acquire an octet.
form a covalent bond.
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© 2013 Pearson Education, Inc. Chapter 5, Section 1 21
Elements That Exist as Diatomic Molecules
These seven elements share electrons to form diatomic, covalent molecules.
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© 2013 Pearson Education, Inc. Chapter 5, Section 1 22
Electron-Dot Formulas for Some Covalent Compounds
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© 2013 Pearson Education, Inc. Chapter 5, Section 1 23
Guide to Drawing Electron-Dot Formulas
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Step 1 Determine the arrangement of atoms. In NH3, N is the central atom and is bonded to three H atoms. Step 2 Determine the total number of valence electrons. Total valence electrons for NH3 = 8 e−
Draw the Electron-Dot Formula for NH3
H N H
H
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Step 3 Attach each bonded atom to the central atom with a pair of electrons.
Draw the Electron-Dot Formula for NH3
H N H
H
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Step 4 Place the remaining electrons using single or multiple bonds to complete the octets. 8 valence e− − 6 bonding e− = 2 e− remaining Use the remaining 2 e− to complete the octet around the N atom.
Draw the Electron-Dot Formula for NH3
H N H
H
H N H
H
or
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© 2013 Pearson Education, Inc. Chapter 5, Section 1 27
Learning Check
Draw the electron-dot formula for CCl4.
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Step 1 Determine the arrangement of atoms. In CCl4, C is the central atom and is bonded to four Cl atoms.
Solution
Cl Cl C Cl
Cl
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Step 2 Determine the total number of valence electrons. Total valence electrons for
Solution
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Step 3 Attach each bonded atom to the central atom with a pair of electrons.
Solution
Cl Cl C Cl
Cl
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Step 4 Place the remaining electrons, using single or multiple bonds to complete the octets.
32 valence e− − 8 bonding e− = 24 e− remaining Use the remaining 24 e− to complete the octets around the Cl atoms.
Solution
Cl Cl C Cl
Cl
or
Cl Cl C Cl
Cl
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Single and Multiple Bonds
In many covalent compounds, atoms share two or three pairs of electrons to complete their octets.
In a single bond, one pair of electrons is shared.
In a double bond, two pairs of electrons are shared.
In a triple bond, three pairs of electrons are shared.
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Step 1 Determine the arrangement of atoms. In CS2, C is the central atom and is bonded to two S atoms.
Draw the Electron-Dot Formula for CS2
S C S
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Step 2 Determine the total number of valence electrons. Total valence electrons for
Draw the Electron-Dot Formula for CS2
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Step 3 Attach each bonded atom to the central atom with a pair of electrons. A pair of bonding electrons (single bond) is placed between each S atom and the central C atom.
Draw the Electron-Dot Formula for CS2
S C S
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Step 4 Place the remaining electrons using single or multiple bonds to complete the octets.
16 valence e− - 4 bonding e− = 12 e− remaining
The remaining 12 electrons are placed as six lone pairs of electrons on both S atoms. However, this does not complete the octet for the C atom.
Draw the Electron-Dot Formula for CS2
S C S
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Step 4 Continued: Double and Triple Covalent Bonds: To complete the octet for the C atom, it
needs to share an additional lone pair from each of the S atoms, forming a double bond with each S atom.
Draw the Electron-Dot Formula for CS2
S C S
or
S C S
S C S
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© 2013 Pearson Education, Inc. Chapter 5, Section 1 38
A Nitrogen Molecule has a Triple Bond
In a nitrogen molecule, N2,
each N atom shares 3 electrons,
each N atom attains an octet, and
the sharing of 3 sets of electrons is called a triple bond.