CHEM 121 Chapter 2 Winter 2015 1. Elements and Symbols Elements: Chemical symbols Ex. cobalt =...
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Transcript of CHEM 121 Chapter 2 Winter 2015 1. Elements and Symbols Elements: Chemical symbols Ex. cobalt =...
CHEM 121
Chapter 2
Winter 2015
1
Elements and Symbols• Elements:• •
• Chemical symbols• •
• Ex. cobalt =
nitrogen =
2
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
3
Some unusual element symbols
• Au
• Ag
• Fe
• Pb
• Cu
4
• Sn
• K
• Na
Reading the Periodic Table
Period: Group:
Alkali metals:
Alkaline earth metals:
Halogens:
5
Noble Gases:
Metals, Nonmetals, and Metalloids
• Metals:• • •
• Nonmetals:• • •
• Metalloids:• B, Si, Ge, As, Sb, Te, At
6
CarbonThree elemental formsInteresting bonding with many elements
7
Diamond Graphite Buckyball
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
8
Elements of Life
9
C N O H
Other life elements
Fluids:
Na
K
Cl
10
Major minerals (macronutrients)
Proteins:
Mg
S
Teeth & Bone:
Ca
P
Trace elements (micronutrients)
Fe Zn I F Se
Molecules
Molecules:Compounds:
Chemical formula:
How many atoms? •NaCl
•H2O
•CsCl2•H2O2
•Ca(OH)211
How many of each type of atom is in one molecule of ammonium phosphate?
12
3-minute practice
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
Atomic Number and Mass Number
• Atomic Number (Z)
14
• Atoms are electrically neutral
• Mass Number (A)
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?
15
3-minute practice
IsotopesIsotopes:
16
Mg
12
24
Atomic Symbol
Isotopes of Carbon12C : 6 protons + 6 neutrons13C : 6 protons + 7 neutrons14C : 6 protons + 8 neutrons
17
98.89 %1.11 %
<0.01 %
All have nearly identical chemical behavior
How many protons, neutrons and electrons does each of the following have?
• 35Cl
• 37Cl
• C-14
18
3-minute practice
Atomic Mass
weighted average of masses of all the naturally occurring isotopes of that element
19
Example: chlorine
35Cl
37Cl
Mass (amu)
x Abundance (%)
Contribution to
average Cl atom
=
x
x
100
78.75
100
22.24
=
=
Relative Masses of Atoms
Atoms are too small to measure actual mass
Compare masses of atoms using relative mass
20
An average Zn atom is ~ 3x more massive than an average Na atom
Medical Use of Isotopes
I-131
21
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-
22
Each e- in an atom “sits” at an energy level (n)• •
•
• •
Energy States• Ground state:
• n = 1
• Excited states: • n = 2, 3, 4,…
• Photon emitted:
• Photon absorbed:
23
Energy Sublevels
• Each level consists of sublevels• # of sublevels in each level = level
number
• n = 1
• n = 2
• n = 3
• n = 4
24
Increasing energy of sublevels within an energy level:
Disneyland Analogy
25
Orbitals
• Regions with the highest probability of finding an electron
• Each type of orbital has a given shape:
26
s orbital
p orbitals
Orbitals
27
d orbitals
Each orbital can hold _____ electrons• s orbitals:
• p orbitals:
• d orbitals:
Orbitalsf orbitals
http://int.ch.liv.ac.uk/Lanthanide/Ln_Chemistry_folder/Miscellaneous%20folder/Miscellaneous.html#f_orbitals 28
• 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?
29
5-minute practice
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
30
1s
Orbital Diagram:
Electron Configurations
31
tell us which orbitals electrons are in for a given atom
Example: Hydrogen Atomic Number: (How many electrons?)
Electron Configuration:
1s
Orbital Diagram:
Electron Configurations
32
Example: Helium Atomic Number: (How many e-?)
Electron Configuration:
1s
Orbital Diagram:
Example: Lithium Atomic Number: (How many e-?)
Electron Configuration:
2s
1s
Orbital Diagram:
Electron Configurations
33
Example: Boron Atomic Number: (How many electrons?)
Electron Configuration:
2s
2p
1s
Orbital Diagram:
Electron Configurations
34
Example: Oxygen Atomic Number: (How many electrons?)
Electron Configuration:
2s
2p
Abbreviated Configuration:
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
35
Sublevel Order
36
Write the abbreviated electron configuration for the following:
• K• S• Br• Ar• Cs
37
5-minute review
Periodic Trends
Valence electrons: • • •
38
Boron (B): How many valence electrons?
Chlorine (Cl):
Periodic Trends
39
Aluminium (Al):
How many valence electrons?
How many valence electrons?
Electron Dot Symbols
40
Lithium Valence electrons?
Carbon Valence electrons?
Fluorine Valence electrons?
Draw electron dot symbols for the following:
•Sulfur
•Potassium
•Beryllium
•Silicon
41
5-minute review
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
42
Atomic radius:
•
•
Atomic Size
43
Ionization:
Ionization Energy
44