THE PERIODIC TABLE
In the mid-1800s many elements have already been discovered. While new ones continued to be discovered, the need for a more accurate way to classify them became evident. Scientists observed that some elements had similar behaviour and properties.
In 1820, J. Döbereiner proposed to group certain elements in triads (groups of three) which presented a gradual variation of some properties from the first element to the last one. Döbereiner explained that the average atomic weight of the extreme elements is like the element in the middle of the triad.
Later, in 1864, J. Newlands proposed to list the elements known so far by their increasing atomic weight. In his research, he observed that similar physical and chemical properties recur at intervals of eight, therefore he grouped them in octets and compared them to octaves in music.
His work was later recognised as the first attempt to classify the elements.
A classification based on the increase of the elements´ atomic mass was published in 1869 independently both by D. Mendeleev and L. Meyer. Mendeleev grouped the elements according to their properties and predicted the existence of elements not yet discovered..
In 1913, H. Moseley corrected certain inconsistencies by reordering the elements by their atomic number (Z) which takes into account the number of protons in each one of them. Furthermore, each element´s position in the periodic table can be related to the characteristics of the atom´s shell.
All chemical elements in the periodic table are arranged into 18 columns called groups or families and 7 horizontal rows, called periods.
All elements in the same group have an equal number of electrons in their valence shell and therefore they have similar chemical properties.
All elements in the same period have the same number of electron shells.
Periodic Table
Mendeleev´s Genius
Focus on Language:
1.- Using the information given in the text and in the videos, please complete the following Quizlet activity. This is a wonderful learning experience that not only allows you to check your pronunciation and spelling but also, by clicking on each one of the tabs, it helps you to study using flash cards and test yourself using different sets of questions:
2.- The activities given below have been designed for you.
Please, choose the area of your preference to exercise and test your knowledge. You are allowed to choose any topic, even if it is not included here. The conditions are the following:
a) the activity you choose has to be related to the periodic table vocabulary and contents,
b) for every topic you choose, you must elaborate a short text expressing your opinions about its importance in chemistry and how it relates to the periodic law. We will share everybody´s opinions in class!
Have fun!!
2.1- Play and learn with these interactive periodic tables. Explore each tab and discover the hidden information behind the elements, listen to the podcasts, watch the videos and learn more about the uses of each element. Enjoy!
The Elements — Descriptions, Uses and Occurrences
2.2- Use the simulation to build an atom out of protons, neutrons, and electrons. Observe the changes in the element, the charge and the mass. Once you´re finished, try the game and test your own theories!
2.3- How abundance relates to the average atomic mass of an element? Use the simulation to learn about isotopes!
2.4- What do you know about radioactive elements? What are they most commonly used for?
IUPAC - Isotopes (International Union of Pure and Applied Chemistry).
2.5- Test yourself!
2.6- Explore the most recent version of the Periodic Table of Elements released by the IUPAC on November 28 2016 including the latest added elements:
Sources:
- IUPAC - Isotopes Matter: http://kcvs.ca/isotopesmatter/iupacMaterials/lessons/home/home.html
- Khan Academy: https://www.khanacademy.org/science/chemistry/
- 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/
- Royal Society of Chemistry: http://www.rsc.org/
