Transcript CHEM121_Lecture_Ch2_student

CHEM 121
Chapter 2
Winter 2015
1
Elements and Symbols
• Elements:
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• Chemical symbols
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• Ex. cobalt =
nitrogen =
2
Elements
1A
8A
2A
• Ordered by atomic number
• “Periodic” trends
• Periodic table by Mendeleev (1871)
3B
4B
5B
6B
7B
8B
1B
3A
4A
5A
6A
7A
2B
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Some unusual element symbols
• Au
• Sn
• Ag
• K
• Fe
• Pb
• Na
• Cu
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Reading the Periodic Table
Period:
Group:
Alkali metals:
Alkaline earth metals:
Halogens:
Noble Gases:
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Metals, Nonmetals, and Metalloids
• Metals:
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• Nonmetals:
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• Metalloids:
• B, Si, Ge, As, Sb, Te, At
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Carbon
Three elemental forms
Interesting bonding with many elements
Diamond
Graphite
Buckyball
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Element Song
• Meet the elements:
http://www.youtube.com/watch?v=Uy0m7jnyv6U&featur
e=related
• All of the elements:
http://www.youtube.com/watch?v=zGMwSKFBpo&feature=related
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Elements of Life
C
N
O
H
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Other life elements
Major minerals (macronutrients)
Fluids:
Proteins:
Teeth & Bone:
Na
Mg
Ca
K
S
P
Cl
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)2
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3-minute practice
How many of each type of atom is in one
molecule of ammonium phosphate?
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Atoms and Subatomic Particles
Diameter of one atom:
0.1 – 0.5 nm
Proton
Neutron
Electron
Charge
Mass (g)
Mass (amu)
Location
amu: atomic mass unit (1/12 C atom mass)
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Atomic Number and Mass Number
• Atomic Number (Z)
• Atoms are electrically neutral
• Mass Number (A)
14
3-minute practice
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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Isotopes
Isotopes:
Atomic Symbol
24
12
Mg
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Isotopes of Carbon
12C
: 6 protons + 6 neutrons
13C : 6 protons + 7 neutrons
14C : 6 protons + 8 neutrons
98.89 %
1.11 %
<0.01 %
All have nearly identical chemical behavior
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3-minute practice
How many protons, neutrons and electrons
does each of the following have?
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35Cl
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37Cl
• C-14
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Atomic Mass
weighted average of masses of all the naturally
occurring isotopes of that element
Example: chlorine
Mass (amu)
35Cl
37Cl
Contribution to
x Abundance (%) = average Cl atom
x
75.78
100
=
x
24.22
100
=
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Relative Masses of Atoms
Atoms are too small to measure actual mass
Compare masses of atoms using relative mass
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 Table
Period: horizontal row
Group: vertical column
Elements in the same group have similar chemical
properties
because they have the same number of outer shell e-
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 
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:
s orbital
p orbitals
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Orbitals
d orbitals
Each orbital can hold
_____ electrons
• s orbitals:
• p orbitals:
• d orbitals:
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Orbitals
f orbitals
http://int.ch.liv.ac.uk/Lanthanide/Ln_Chemistry_folder/Miscellaneous%20folder/Miscellaneous.html#f_orbitals
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5-minute practice
• 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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Orbital Energy Levels
• Pauli Exclusion Principle:
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• 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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Electron Configurations
tell us which orbitals electrons are in for a given atom
Example: Hydrogen
1s
Atomic Number:
(How many electrons?)
Orbital Diagram:
Electron Configuration:
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Electron Configurations
Example: Helium
Atomic Number:
(How many e-?)
1s
Orbital Diagram:
Electron Configuration:
Example: Lithium
1s
Atomic Number:
2s
(How many e-?)
Orbital Diagram:
Electron Configuration:
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Electron Configurations
Example: Boron
Atomic Number:
(How many electrons?)
1s
2s
2p
Orbital Diagram:
Electron Configuration:
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Electron Configurations
Example: Oxygen
Atomic Number:
(How many electrons?)
1s
2s
2p
Orbital Diagram:
Electron Configuration:
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
36
5-minute review
Write the abbreviated electron configuration for
the following:
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K
S
Br
Ar
Cs
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Periodic Trends
Valence electrons:
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Boron (B):
How many valence electrons?
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Periodic Trends
Aluminium (Al):
How many valence electrons?
Chlorine (Cl):
How many valence electrons?
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Electron Dot Symbols
Lithium
Valence electrons?
Carbon
Valence electrons?
Fluorine
Valence electrons?
40
5-minute review
Draw electron dot symbols for the following:
• Sulfur
• Potassium
• Beryllium
• Silicon
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Elements
1A
8A
2A
• Elements ordered by atomic number
• “Periodic” trends
• Periodic table by Mendeleev (1871)
3B
4B
5B
6B
7B
8B
1B
3A
4A
5A
6A
7A
2B
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Atomic Size
Atomic radius:
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Ionization Energy
Ionization:
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