chem 121 chapter 2 winter 2015 1. elements and symbols elements: chemical symbols ex. cobalt =...
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CHEM 121
Chapter 2
Winter 2015
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Elements and Symbols• Elements:• •
• Chemical symbols• •
• Ex. cobalt =
nitrogen =
2
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Elements• Ordered by atomic number• “Periodic” trends• Periodic table by Mendeleev (1871)
1A 2A
3B 4B 5B 6B 7B 8B 1B 2B
3A 4A 5A 6A 7A
8A
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Some unusual element symbols
• Au
• Ag
• Fe
• Pb
• Cu
4
• Sn
• K
• Na
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Reading the Periodic Table
Period: Group:
Alkali metals:
Alkaline earth metals:
Halogens:
5
Noble Gases:
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Metals, Nonmetals, and Metalloids
• Metals:• • •
• Nonmetals:• • •
• Metalloids:• B, Si, Ge, As, Sb, Te, At
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CarbonThree elemental formsInteresting bonding with many elements
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Diamond Graphite Buckyball
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Element Song• Meet the elements: http://www.youtube.com/watch?v=Uy0m7jnyv6U&feature=related
• All of the elements: http://www.youtube.com/watch?v=zGM-wSKFBpo&feature=related
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Elements of Life
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C N O H
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Other life elements
Fluids:
Na
K
Cl
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Major minerals (macronutrients)
Proteins:
Mg
S
Teeth & Bone:
Ca
P
Trace elements (micronutrients)
Fe Zn I F Se
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Molecules
Molecules:Compounds:
Chemical formula:
How many atoms? •NaCl
•H2O
•CsCl2•H2O2
•Ca(OH)211
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How many of each type of atom is in one molecule of ammonium phosphate?
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3-minute practice
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Atoms and Subatomic Particles
Proton Neutron Electron
Diameter of one atom: 0.1 – 0.5 nm
13amu: atomic mass unit (1/12 C atom mass)
Charge
Mass (g)
Mass (amu)
Location
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Atomic Number and Mass Number
• Atomic Number (Z)
14
• Atoms are electrically neutral
• Mass Number (A)
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How many protons, electrons, and neutrons are in each of the following:
•Z = 14 A= 29
•An atom with a nucleus with 4 protons and 5 neutrons?
•A potassium atom with a mass number of 39?
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3-minute practice
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IsotopesIsotopes:
16
Mg
12
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Atomic Symbol
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Isotopes of Carbon12C : 6 protons + 6 neutrons13C : 6 protons + 7 neutrons14C : 6 protons + 8 neutrons
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98.89 %1.11 %
<0.01 %
All have nearly identical chemical behavior
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How many protons, neutrons and electrons does each of the following have?
• 35Cl
• 37Cl
• C-14
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3-minute practice
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Atomic Mass
weighted average of masses of all the naturally occurring isotopes of that element
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Example: chlorine
35Cl
37Cl
Mass (amu)
x Abundance (%)
Contribution to
average Cl atom
=
x
x
100
78.75
100
22.24
=
=
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Relative Masses of Atoms
Atoms are too small to measure actual mass
Compare masses of atoms using relative mass
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An average Zn atom is ~ 3x more massive than an average Na atom
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Medical Use of Isotopes
I-131
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Reading the Periodic TablePeriod: horizontal row Group: vertical column
Elements in the same group have similar chemical propertiesbecause they have the same number of outer shell e-
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Each e- in an atom “sits” at an energy level (n)• •
•
• •
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Energy States• Ground state:
• n = 1
• Excited states: • n = 2, 3, 4,…
• Photon emitted:
• Photon absorbed:
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Energy Sublevels
• Each level consists of sublevels• # of sublevels in each level = level
number
• n = 1
• n = 2
• n = 3
• n = 4
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Increasing energy of sublevels within an energy level:
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Disneyland Analogy
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Orbitals
• Regions with the highest probability of finding an electron
• Each type of orbital has a given shape:
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s orbital
p orbitals
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Orbitals
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d orbitals
Each orbital can hold _____ electrons• s orbitals:
• p orbitals:
• d orbitals:
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Orbitalsf orbitals
http://int.ch.liv.ac.uk/Lanthanide/Ln_Chemistry_folder/Miscellaneous%20folder/Miscellaneous.html#f_orbitals 28
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• How many sublevels are in the n = 3 energy level?
• What are these sublevels? How many of each type are there?
• How many electrons can be held in the n = 3 energy levels?
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5-minute practice
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Orbital Energy Levels• Pauli Exclusion Principle:
•
• Electrons want to sit in lowest energy level
• For a given n value: Order of sublevel energy: s < p < d < f
• Orbital Diagrams
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1s
Orbital Diagram:
Electron Configurations
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tell us which orbitals electrons are in for a given atom
Example: Hydrogen Atomic Number: (How many electrons?)
Electron Configuration:
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1s
Orbital Diagram:
Electron Configurations
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Example: Helium Atomic Number: (How many e-?)
Electron Configuration:
1s
Orbital Diagram:
Example: Lithium Atomic Number: (How many e-?)
Electron Configuration:
2s
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1s
Orbital Diagram:
Electron Configurations
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Example: Boron Atomic Number: (How many electrons?)
Electron Configuration:
2s
2p
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1s
Orbital Diagram:
Electron Configurations
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Example: Oxygen Atomic Number: (How many electrons?)
Electron Configuration:
2s
2p
Abbreviated Configuration:
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Electron Configurations relate to the Periodic Table!
• s block elements: end with s orbital
Na:
• p block elements: end with p orbitals
P:
• d block elements: end with d orbitals
Ni:
Note: 4s orbital comes before 3d orbital
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Sublevel Order
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Write the abbreviated electron configuration for the following:
• K• S• Br• Ar• Cs
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5-minute review
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Periodic Trends
Valence electrons: • • •
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Boron (B): How many valence electrons?
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Chlorine (Cl):
Periodic Trends
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Aluminium (Al):
How many valence electrons?
How many valence electrons?
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Electron Dot Symbols
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Lithium Valence electrons?
Carbon Valence electrons?
Fluorine Valence electrons?
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Draw electron dot symbols for the following:
•Sulfur
•Potassium
•Beryllium
•Silicon
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5-minute review
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Elements• Elements ordered by atomic number• “Periodic” trends• Periodic table by Mendeleev (1871)
1A 2A
3B 4B 5B 6B 7B 8B 1B 2B
3A 4A 5A 6A 7A
8A
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Atomic radius:
•
•
Atomic Size
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Ionization:
Ionization Energy
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