Transcript Chemistry 103

Chemistry 103
Lecture 9
Outline
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I. Chemical Bonds - Ionic Compounds (CH6)
 Electron Dot Symbols
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Lewis Dot Diagrams
Predicting Formulas
Bonds
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Chemical bond: attractive force holding
two or more atoms together.
Bonds
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Ionic Bonds - electron transfer process.
Typically between a metal and a nonmetals
Covalent Bonds - electrons shared.
Typically involving nonmetals.
The Representative Elements
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Publishing as Benjamin Cummings
Rules for Electron Dot Symbols
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1. Representative elements in the same
group of the periodic table have the same
number of valence electrons
2. The number of valence electrons is
represented by “dots” around the symbol of
the representative element.
3. The maximum number of valence
electrons for any representative element is 8
- Octet Rule.
Learning Check - Aluminum (Al)
1. Number of valence electrons in aluminum is:
A) 1
B) 2
C) 3
2. In Al, the change in electrons to achieve an octet is:
A) loss of 3eB) gain of 3e- C) a gain of 5e-
3.
The Ionic charge of aluminum is:
A) 3B) 5-
4. The symbol for the aluminum ion is:
A) Al3+
B) Al3-
C) 3+
C) Al+
Learning Check
1. Number of valence electrons in sulfur is:
A) 4eB) 6eC) 8e2. Change in electrons for octet requires a:
A) loss of 2eB) gain of 2eC) a gain of 4e3. Ionic charge of sulfur is:
A) 2+
B) 2-
C) 4-
Predicting Ionic Charge
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The number of electrons an atom loses is related to its position
on the periodic table.
The Periodic Table and Ions
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Group IA metals - +1
Group IIA metals - +2
Group IIIA metals - +3
Group VIIA nonmetals - -1
Group VIA nonmetals - -2
Group VA nonmetals - -3
Salt is An Ionic Compound
Sodium chloride in “table salt” is an example of an ionic
compound. Chemical Formula: NaCl
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Publishing as Benjamin Cummings
11
Chemical Formulas
of Ionic Compounds
For a neutral species, the number of electrons lost
and gained must be equal.
•
The amount of positive charge must equal the
amount of negative charge.
Formulas of ionic compounds
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Symbol for the positive ion is always written first
The charges on the ions are NOT shown in the
formula
The subscripts in the formula give the combining
ratio for the ions
Lewis Dot Diagrams
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Using the Electron Dot Symbols, write the
Lewis Dot Diagram and the Chemical
Formula for
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Na and Cl
Ionic Formula of NaCl
In an ionic formula,
• The symbol of the metal is written first followed by the
symbol of the nonmetal
• The charges of the ions in the compound are not shown
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Lewis Dot Diagrams continued…
•
Example: What is the Lewis Dot Diagram
and the chemical formula for the ionic
compound formed between Mg and Cl?
Charge Balance In MgCl2
In MgCl2
• An Mg atom loses
two valence
electrons
• Two Cl atoms each
gain one electron
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Dot Diagrams & Chemical Formulas
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Write the Lewis Dot Diagrams and give
the chemical formulas for the ionic
compounds formed between the following
elements
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Na and O
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Ca and O
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Al and O
Writing Ionic Formulas from Charges
Charge balance is used to write the formula for
sodium nitride, a compound containing Na+ and N3−.
3
Na+
Na+
Na+
3(+1) + 1(3-)
N3-
=
=
0
Na3N
Ionic Chemical Formulas
Give the chemical formula for the ionic
compounds made from the following
elements:
1. K and F
2. Mg and S
3. Al and S
4. Li and N
Chapter 2 - Measurements
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Measurements
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Sig Figs”
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Identifying
Rounding
Math Operations
Dimensional Analysis
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Percent Factor
Density
Chapter 3 - Matter (and Energy)
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Chemical vs.Physical
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Matter Classified
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Element
Compound
Homogeneous Mixture
Heterogeneous Mixture
Chapter 4 - Atoms & Elements
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Periodic Table
Symbols for Elements
The Atom
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Atomic Symbols
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History
Subatomic Particles
Isotopes, Ions
Atomic Mass (amu)
Chapter 5 (Ch4) - Electronic Structure
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Electromagnetic
Radiation
Classical vs Quantum
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History
Quantum Numbers
Electron Configurations
Orbital Diagrams
Valence
Atomic Radii
Practice Problem
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The density of diamond
is 3.51g/mL. What is
the volume (in liters) of
the Hope diamond if it
has a mass of 44.0
carats?
(1 carat = 0.200g)
Practice Multiple Choice
1). Which species has 16 neutrons?
a. 31P
b. 34S2-
c. 36Cl
d. 89Br-
(p = 15)
(p = 14)
(p=17)
(p=35)
e. none of these
2). An isotope of which element is used as the standard for the relative mass
scale for atoms?
a. nitrogen
b. oxygen
c. hydrogen
d. gold
e. none of these
Practice Multiple Choice
3). Which of the following elements is expected to be chemically similar to calcium (Ca).
a. K
b. Sc
c. Cl
d. Mg
e. Al
4). A g-orbital has an “l” quantum number of 4. How many total electrons can this subshell hold?
a. 4
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b. 6
c. 18
d. 10
l = 4, ml = -4,-3,-2,-1,0,1,2,3,4 (9 values = 9 orbitals x 2 = 18 electrons)
e. 14