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~William Lawrence Bragg

Periodic Table Simulator

How Mendeleev Did It. Fall 2009

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 In the first part of the activity,
you will group playing cards by
pattern by suit and numerical value. Compare your
their “properties,” that is by suit
results to your neighbor’s. Make a and rank. In the second part of
table in your lab journal to the activity, you will group
elements by chemical properties
summarize your results. and atomic weight. Finally,
you will graph selected periodic
More inside!
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 Graphing Periodic Trends
you used for groups #1 and #2. Again, look for
patterns and gaps. Identify where in your table a Use internet resources to find the
atomic radius, electronegativity and
missing element should appear. Predict its properties first ionization energy for elements 1-
(suit and value). Record your predictions and find the 56.

missing card in the Undiscovered Elements envelope. Create a spreadsheet with atomic
Make a table in your lab journal to summarize your number, element name, element
symbol and the properties listed above.
Use your spreadsheet to create three
graphs showing the relationship
Based on what you know about Mendeleev’s work,
what are the connections between what you did with Atomic radius and atomic number

the playing cards and what Mendeleev did when First ionization energy and atomic
making his periodic table? Discuss with you lab number

partners and write a brief statement comparing the card Electronegativity and atomic number.
activity with Mendeleev’s work.
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.

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,
Julius Lothar Meyer arrange each element in the group in order of
increasing atomic weight, lightest on top and heaviest
Mendeleev published his periodic table of all known
on bottom. Repeat for each oxygen combination
elements in 1870. Working completely
independently, a few months later, Meyer published
a revised and expanded version of his 1864 table, With each group in a stack (lightest element on top),
virtually identical to that published by Mendeleev, arrange the stacks in order of increasing atomic
and a paper showing graphically the periodicity of weight, lightest on the left to heaviest on the right.
the elements as a function of atomic weight.
Expand the ranked groups into a rectangular table.
Meyer’s and Mendeleev’s work , and the following Leave spaces in the table as needed to maintain the
supporting evidence from other researchers led to sequence of increasing atomic weight.
the development of modern periodic law.

Mendeleev predicted the existence What do the gaps represent? Make predictions about
of several undiscovered elements. the properties of the missing elements. Write your
“Eka-silicon” was discovered in predictions in your lab journal, and “discover” the
1886 by Winkler. The properties missing elements. How close were your predictions?
predicted by Mendeleev match the
actual properties closely.

When arranged by atomic number,

the tellurium-iodine problem was

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.

Tragically for the development of science, Moseley was

killed in action at Gallipoli in 1915.

Accounting for Transition Elements

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
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.


Talk it out with your lab partners. Remember—understanding

is more important than answering!

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