Download 9-16-09 Periodic Table

Chem 105
John Keller
Mon. 9-16-09
Today
Isotope practice problem
Periodic Table
Cations
Anions
Mon 9-16-09
Announcements
Please EMAIL any new or changed
clicker serial numbers to
[email protected].
Please use the HALLWAY KIOSK
outside of 194 Reichardt 24x7 to
check your clicker function and
registration.
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Mon 9-16-09
36%
23%
14%
8%
7%
2
1%
7
5
4
3
2%
6
8%
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This is the Participant Number chart for KELLER
MWF 2:15-3:15. If you click your clicker here, and it
is registered in the database on this computer, it
should also light up in class.
No
Yes
No
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3
4
5
6
7
Ye
s
1.
2.
3.
4.
5.
6.
7.
8.
Isotope % practice problem from OWL
Mon 9-16-09
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The element lithium has an atomic weight of 6.94 and consists of two
stable isotopes lithium-7 and lithium-6.
The isotope lithium-7 has an atomic mass of 7.02 amu and a percent
natural abundance of 92.6%.
The isotope lithium-6 has a percent natural abundance of 7.42%.
What is the atomic mass of lithium-6?
____________amu
One interpretation of this phrase is:
“A mole of lithium atoms (from
nature) has a mass of 6.94 g.”
Mon 9-16-09
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A natural lithium atom has a mass of 6.94 amu.
1. True
2. False
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Mon 9-16-09
ls
e
Fa
Tr
ue
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A natural lithium atom has a mass of 6.94 amu.
1. True
2. False
6.94 g is the mass of a mole of natural lithium, which
contains about 93% of Li-7 and about 7% of Li-6 atoms.
There is no such thing as a “natural lithium atom”. No
particle has a mass of 6.94 amu.
Mon 9-16-09
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The element lithium has an atomic weight of 6.94 and consists of
two stable isotopes lithium-7 and lithium-6.
The isotope lithium-7 has an atomic mass of 7.02 amu and a
percent natural abundance of 92.6%.
The isotope lithium-6 has a percent natural abundance of 7.42%.
What is the atomic mass of lithium-6?
Mon 9-16-09
____________amu
7
Fraction 7Li = % 7Li ÷ 100 = 0.926 moles 7Li/mole nat Li
Fraction 6Li = % 6Li ÷ 100 = 0.0742 moles 6Li/mole nat Li
Mass of 7Li/ mol nat Li + mass 6Li/ mol nat Li = 6.94 g/mol nat Li
 7.02 g 
 x 
6


 = 6.94 g
×
+
×
0.926 mol Li 
0.0742 mol Li 

7
6
 mol Li 
 mol Li 
7
Or
0.926 mol 7Li  7.02 g  0.0742 mol 6Li  x 
6.94 g
×
+
=
mol nat Li  mol 7Li 
mol nat Li  mol 6Li  mol nat Li
0.926 * 7.02 = 6.50052
The product of 0.926 and 7.02 has 3 sig figs.
(underlined). When you subtract that number
from 6.94, the answer has the last significant
6.94000
decimal in the “hundredths” column. So even
− 6.50052
though both addends have 3 sig figs, the
0.43948
answer has only 2. This often happens when
two numbers that are close in value are
subtracted – you lose information! Then in the
0.43948
= 5.9229 g = 5.9 g last division, the 2-sig-fig numerator requires
0.0742
that the answer also have 2-sig figs.
Mon 9-16-09
0.926(7.02) g + 0.0742 x = 6.94 g
6.94 − 0.926(7.02)
g
0.0742
x = 5.923 g = 5.9 g
x=
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Periodic Table
Mon 9-16-09
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Periodic Table of the Elements
1) See www.webelements.com
2) Tom Lehrer
3) Periodic table
http://www.privatehand.com/flash/elements.html
Mon 9-16-09
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“American system” of numbering groups
1A 2A
Non-metals (incl H)
3B 4B 5B 6B 7B ----8B----- 1B 2B 3A 4A 5A 6A 7A 8A
metalloids
metals
Inert gases
See wall periodic tables
Mon 9-16-09
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FAQ: In Chem 105, do I have to memorize the names and formulas of the elements?
Yes, some of them, as shown below. Exams will contain a periodic table, but no
names.
Why? The American Chemical Society standard final exam expects you to know
that, for example, the symbol for potassium is K, and not Po!
1A 2A
3B 4B 5B 6B 7B ----8B----- 1B 2B 3A 4A 5A 6A 7A 8A
Please know names and
formulas of the elements
inside the red box.
Mon 9-16-09
…especially the “C’s”!
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“Main Group” elements
1A 2A
Mon 9-16-09
3B 4B 5B 6B 7B ----8B----- 1B 2B 3A 4A 5A 6A 7A 8A
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1A 2A
3B 4B 5B 6B 7B ----8B----- 1B 2B 3A 4A 5A 6A 7A 8A
“Transition” elements
Mon 9-16-09
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1A 2A
3B 4B 5B 6B 7B ----8B----- 1B 2B 3A 4A 5A 6A 7A 8A
Lanthanides & Actinides
Mon 9-16-09
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Alkali metals: exothermic reaction with water
2 Na + H2O H2 + 2 NaOH + heat
Mon 9-16-09
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Winner of the 2002 Ig Nobel Prize in Chemistry –
Theodore Gray and his hand-carved periodic table.
http://www.theodoregray.com/PeriodicTable/index.html
(Check out “sodium party” link at this web site.)
Mon 9-16-09
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Excellent book! Personal
history of the young
Oliver Sacks who as a
kid was fascinated by
the Periodic Table.
$10 from Amazon.com
Mon 9-16-09
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Alkaline earth metals
Halogens
These elements exist as
diatomic molecules X2
Mon 9-16-09
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-Cations
-Anions
-Ionic Compounds
Mon 9-16-09
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Ionic compounds contain CATIONS (+) and ANIONS (-).
CATION “CAT-eye-on” The “t” looks like “+” CA+ION.
ANION
“AN-eye-on”
(opposite charge from cation)
The whole compound is electrically neutral.
Total amount of (+) charge = total amount of (-) charge.
Mon 9-16-09
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CATIONS
Metals form exclusively IONIC compounds, as Cations (+).
Metal atoms in Groups 1A, 2A, and 3A lose electrons to form “inert
gas configuration”. That is, same number of electrons as the NEXT
SMALLER inert gas.
1A 2A
3A
Mon 9-16-09
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Potassium ion K+ forms from K atom by…
Adding a positron (+1)
Removing an electron (-1)
Adding two positrons and removing
one electron.
75
9
po
s.
...
el
in
g
dd
A
em
ov
R
tw
in
g
o
an
po
si
a
in
g
dd
A
Mon 9-16-09
..
4
t..
.
1.
2.
3.
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Potassium ion K+ forms from K atom by…
1.
2.
3.
Adding a positron (+1)
Removing an electron (-1)
Adding two positrons and removing
one electron.
Positrons exist (inside accelerators), but have almost nothing
to do with chemistry.
K atom contains 19 protons (+19) in the nucleus and 19
electrons. When you remove an electron, there are still 19
protons, but only 18 electrons. 19 – 18 = +1
Mon 9-16-09
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Group 1 atoms: Li Li+ + one electronLi+ has the same number of electrons as He atom.
Mon 9-16-09
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Group 2 atoms: Mg Mg2+
configuration.
Mon 9-16-09
which has Neon electron
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What is the charge on a barium (Ba)
ion (as commonly found in nature)?
55
-2
-1
0
+1
+2
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Mon 9-16-09
2
0
1
8
6
-1
6
-2
1.
2.
3.
4.
5.
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What is the charge on a barium ion
(Ba) (as commonly found in nature)?
1.
2.
3.
4.
5.
-2
-1
0
+1
+2
All group 2A elements, including Mg,
form the +2 ion in compounds.
Mon 9-16-09
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Transition metals have various
charges: from +1 to +4.
Mon 9-16-09
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Cations, continued.
The ONLY non-metal, polyatomic cation we
will encounter is ammonium ion NH4+.
Hydrogen ion
H+
NH4+
NH3
Mon 9-16-09
Ammonia
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Anions
-monatomic anions
-polyatomic anions
Mon 9-16-09
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These elements occur as monatomic anions Xy
y=
-3 -2 -1
NAME: N3- is Nitride Nitrogen
Mon 9-16-09
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Polyatomic ions - like a molecule, but with total charge > or < 0.
All but two contain O, so they are called “oxoanions”.
You need to KNOW NAMES and FORMULAS of these ions. This is
your chemistry vocabulary. Table 2.4 p. 107 And Oxoanion Table
on the course website.
+1
-1
OH(hydroxide)
NO2- (nitrite)
NO3- (nitrate)
ClO- (hypochlorite)
ClO2- (chlorite)
ClO3- (chlorate)
ClO4- (perchlorate)
CN(cyanide)
CH3CO2- (acetate)
MnO4- (permanganate)
HCO3- (hydrogen carbonate)
HSO4- (hydrogen sulfate)
Mon 9-16-09
H2PO4- (dihydrogen phosphate)
NH4+
-2
CO32- (carbonate)
SO32- (sulfite)
SO42- (sulfate)
CrO42- (chromate)
Cr2O72(dichromate)
HPO42- (hydrogen
phosphate)
-3
PO43(phosphate)
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Compounds
y=
-3 -2 -1
Ionic compound between lithium and sulfur: Li2S
Lithium ALWAYS forms 1+ cation. Sulfur ALWAYS forms (in
monatomic ions anyway 2- anion. Therefore need 2x as many Li as S.
Mon 9-16-09
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