By the middle of the 19th century, a great
number of chemical elements had been discovered and scientists needed a more
precise way to classify them. As new elements continued to be discovered,
scientists observed that some elements had similar properties, such as
chlorine, bromine and iodine or calcium, strontium and barium.
In 1817, J.Döbereiner revealed the similarities
between the properties of certain groups of three elements, with a gradual
variation of these properties from the first element to the last one. These groups of three
elements were called triads. To classify them, Döbereiner explained that the
average atomic weight of the weights of the extreme elements, is like the
element in the middle of the triad.
Later, in 1864, J.A.R. Newlands listed the elements
increasing their atomic weight. He noticed that similar physical and chemical
properties recur at intervals of eight and he grouped known elements with
similar properties into groups of eight. He compared this grouping to octaves
in music. Initially, his work was not accepted by the scientific community, but
was later recognised as the first attempt to classify the elements.
In 1869, D. Mendeleev and L. Meyer independently
published a classification of the elements considering the increase of the
atomic mass of the elements and grouping elements together according to their
properties. This classification presented several limitations which were
improved by H. Moseley in 1913. The Moseley table orders the element by their
atomic number (Z), that is, using the number of protons of the elements. Moreover,
the position of each element in the periodic table can be related to the
characteristics of the atom’s shell. The chemical elements are arranged into:
- 18 columns, called groups or families: all elements in the same group have an equal number
of electrons in their valence shell and therefore they have similar chemical
properties.
- 7 horizontal rows, called periods: all elements in the same period have the same number
of electron shells.
ACTIVITIES:
The following activities are presented in different
blocks related to different areas. You can choose which area or activity you
prefer working on or, you can choose another area for your research. Make a
little report with the information you consider relevant and give your opinion
about it. Enjoy it!
Focus on English! Look for the idioms related to the word “table”.
Focus on English! Look for the idioms related to the word “table”.
Physics and chemistry:
You can play and learn with this interactive periodic
table and discover the hidden information behind the elements. You can learn
more about the uses of each element, It´s up to you! (Element Uses)
In this simulation, you can build an atom out of protons, neutrons,
and electrons, and see how the element, charge, and mass change. Then play a
game to test your ideas!
Use the simulation to learn about isotopes and how abundance
relates to the average atomic mass of an element.
- Radioactive elements:
search information about one or more radioactive elements and their uses in
our society.
Maths:
- Choose the element
you prefer to work with and look for the information you need to calculate
their average atomic mass (weighted mass).
Medicine:
- Look for the elements
used in different kind of therapies like radiotherapy or chemotherapy.
- Search for
information about which elements are used to make medicines, implants,
pharmacology…
Biology:
- Search the necessary
elements for a balanced diet.
- Look for which
elements are relevant for animals and plants and make a table with their similarities
and differences.
- Look for which
elements are dangerous for life (animals and plants).
- Which animals have poisoned
protection? Which elements are involved in it?
Geology:
- Look for elements
used in jewellery.
- Search which elements
are relevant in geology, or which are the most abundant elements in Earth.
History:
- Which elements are
used to know the age of the different discoveries in archaeology?
Technology/Engineering:
- Look for the elements
needed for doing a watch, laptop, iPhone, tablet, battery, etc.
- Which elements are
useful in aeronautics, vehicles, buildings, energy systems…?
Music/Art:
- Look for information
about which elements are the best for doing different instruments like a
flute, saxophone, etc.
- Search information
about the elements used for doing different colours or for the conservation
of the artwork, etc.
At home or in your school:
- Look for the elements we use in our daily life or we have around us at home or at school.
Sources of information:
- Physics
and chemistry. 3th Secondary Education. Grupo Anaya, 2015.
- The
periodic table of the elements, in pictures and words. Keith Enevoldsen http://elements.wlonk.com/ElementsTable.htm
- Periodic
table in https://en.wikipedia.org/wiki/Periodic_table
- Phet Simulations in https://phet.colorado.edu/
