periodic table simulator
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The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them. ~William Lawrence Bragg
Periodic Table Simulator
Introduction Dmitri Ivanovich Mendeleev organized the known elements, and predicted some unknown elements, by grouping according to similar properties. We’ll simulate the methods Mendeleev used to make
the modern periodic table. First, we’ll organize
playing cards by suit order (hearts, spades, diamonds)
and numerical value (aces low to kings high). Separate
card group #1 from your stack of playing cards. The
big green number 1 on the back indicates the card
belongs to group #1. Group cards in a rectangular
pattern by suit and numerical value. Compare your
results to your neighbor’s. Make a
table in your lab journal to
summarize your results.
Fall 2009 How Mendeleev Did It.
More inside!
In the first part of the activity, you will group playing cards by their “properties,” that is by suit and rank. In the second part of
the activity, you will group elements by chemical properties
and atomic weight. Finally, you will graph selected periodic
trends.
Summary
2
Find group #2 and arrange the cards in the same
manner. Do you notice a gap? Predict the value and
suit of the missing card. Once you make your
prediction, remove the missing card from the envelope
marked “Undiscovered Elements.” Did your
prediction match the unknown card? Make a table in
your lab journal to summarize your results.
On to card group #3! Repeat the ordering sequence
you used for groups #1 and #2. Again, look for
patterns and gaps. Identify where in your table a
missing element should appear. Predict its properties
(suit and value). Record your predictions and find the
missing card in the Undiscovered Elements envelope.
Make a table in your lab journal to summarize your
results.
Based on what you know about Mendeleev’s work,
what are the connections between what you did with
the playing cards and what Mendeleev did when
making his periodic table? Discuss with you lab
partners and write a brief statement comparing the card
activity with Mendeleev’s work.
Graphing Periodic Trends
Use internet resources to find the atomic radius, electronegativity and first ionization energy for elements 1-56. Create a spreadsheet with atomic number, element name, element symbol and the properties listed above. Use your spreadsheet to create three graphs showing the relationship between: Atomic radius and atomic number First ionization energy and atomic number Electronegativity and atomic number. Look for patterns. How can you use the periodic table to predict properties?
The Tellurium Dilemma When Mendeleev arranged the elements in order of increasing atomic weight, he found that tellurium and iodine ended up in the wrong groups. Iodine (atomic weight = 126.9 AMU) would be placed before tellurium (atomic weight = 127.6 AMU). However, the chemical and physical properties of iodine matched the properties of fluorine, chlorine and bromine. So Mendeleev decided to place iodine with the other halogens, rather than with the oxygen group. It turned out to be the correct grouping, because Moseley re-ordered the periodic table by atomic number several years later.
3
Create your own periodic table!
Get the element cards. They’re the smaller cards with
the names and symbols of the elements on them.
Find the oxygen combination ratio on one of the
cards. You should see something like 2:3 or 1:2.
Group the cards by oxygen combination ratio—that
is, get all the 2:3 elements in the same pile, all the 2:7
elements in the same pile, and so on. Once you have
the cards grouped by oxygen combination ratio,
arrange each element in the group in order of
increasing atomic weight, lightest on top and heaviest
on bottom. Repeat for each oxygen combination
group.
With each group in a stack (lightest element on top),
arrange the stacks in order of increasing atomic
weight, lightest on the left to heaviest on the right.
Expand the ranked groups into a rectangular table.
Leave spaces in the table as needed to maintain the
sequence of increasing atomic weight.
What do the gaps represent? Make predictions about
the properties of the missing elements. Write your
predictions in your lab journal, and “discover” the
missing elements. How close were your predictions?
Julius Lothar Meyer
Mendeleev published his periodic table of all known
elements in 1870. Working completely
independently, a few months later, Meyer published
a revised and expanded version of his 1864 table,
virtually identical to that published by Mendeleev,
and a paper showing graphically the periodicity of
the elements as a function of atomic weight.
Meyer’s and Mendeleev’s work , and the following
supporting evidence from other researchers led to
the development of modern periodic law.
Mendeleev predicted the existence
of several undiscovered elements.
“Eka-silicon” was discovered in
1886 by Winkler. The properties
predicted by Mendeleev match the
actual properties closely.
1.
2.
3.
When arranged by atomic number,
the tellurium-iodine problem was
resolved.
The periodic table was developed by
grouping elements by physical
properties. It also shows grouping
by valence electron configuration.
Henry Moseley’s Contributions Henry Moseley (1887-1915): A British chemist, Henry Moseley studied under Rutherford and brilliantly developed
the application of X-ray spectra to study atomic structure; Moseley's discoveries resulted in a more accurate
positioning of elements in the Periodic Table. In 1913, almost fifty years after Mendeleev, Henry Moseley published
the results of his measurements of the wavelengths of the X-ray spectral lines of a
number of elements which showed that the
ordering of the wavelengths of the X-ray
emissions of the elements coincided with the
ordering of the elements by atomic number.
With the discovery of isotopes of the elements, it
became apparent that atomic weight was not the
significant player in the periodic law, but rather,
the properties of the elements varied periodically
with atomic number.
Accounting for Transition Elements
Tragically for the development of science, Moseley was
killed in action at Gallipoli in 1915.
Look at your table. Without referring to a periodic table, what differences do you notice? Look at one column. Find the “transition property” for the elements in the column. Remove the three elements (two from the fluorine group) that don’t match the others. NOTE: You cannot remove the first card from a column.
Order the removed elements so each group of three is arranged by increasing atomic weight (lightest on top, heaviest on bottom). Arrange each group of three (or two) left to right in order of increasing atomic weight. You should now have two “tables.”
Look at the original elements. Ideally, they will still be arranged by increasing atomic weight from left to right and top to bottom. Find where you can insert the “transition” part of the table into the original table while maintaining the order of increasing atomic weight.
Your table should now look familiar. Compare your table to the modern periodic table. Discuss with your partners—see if you can find similarities and differences. Make a table in your lab journal to summarize your results.
Problems? Talk it out with your lab partners. Remember—understanding is more important than answering! Remember you can visit the tutor room or contact me through e-mail.
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