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THE PERIODIC TABLE

The Periodic Table of the Elements is one of the fundamental tools that all chemistry students should know because it summarizes much of the information that today is known about the different constituents of all matter. This two-hours CLIL lesson is designed to introduce the basic concepts needed to undestan how well-known chemical elements are organized.

  Session 1 (1 hour)                                                                                                                                                              

Activity 1.1. First of all, you must write the answers to the following questions:

                  1- Have you previously studied the Periodic Table?

                  2- Can you list the name of any chemical element included in the Periodic Table?

                  3- What do you think chemical elements are?

                  4- How many different chemical elements are known nowadays?

                  5- Do you think it will be very difficult to learn the names of all the elements of the Periodic Table?

Once you have reflected on what your first impressions about the topic of this lesson, the following video might change your previous answers:

Activity 1.2. As you have checked, learning the names of the chemical elements should not be as difficult as it might seen if even a 3-years-old girl is able to remember all of them. The only thing you need is to relate each element to its one- or two-letter code called Chemical Symbol. To complete this aim, you can start with the 36 most common chemical elements in TASK 1 and then study the complete set of 118 elements in TASK 2.

Activity 1.3. As a final part of this first session, the video presented below is a proposal to memorize the chemical elements, their symbols and the order in which they apperar in the Periodic Table in a more interesting manner. It would be interesting to write by hand the lyrics of this song to practice all what has been learned so far.

  Session 2 (1 hour)                                                                                                                                                              

Activity 2.1. The video in activity 1.3., besides presenting the chemical elements that we must know, also includes the name of some of the Groups or Families which constitute the Periodic Table. To know more about how the chemical elements are classified, you can perform TASK 3. If you need any help, you may watch the following explanatory video:

Activity 2.2. The origin of the elements' classification in the Periodic Table goes back to the beginning of humanity when human beings began to isolate metals. Over the centuries and the increase in the number of known elements, scientists needed to order tham, so that different criteria were proposed. Read the following text and answer the questions below:

The Periodic Table includes a place for all the elements that have been discovered: metals are found on the left and nonmetals on the right and elements with similar properties are grouped together in columns. But the elements haven't always been arranged in this way. It was in 1869 that the brilliant Russian scientist Dmitri Mendeleev worked out the basis of the modern periodic table. He was a fanatical card player; his favorite game was patients. By Mendeleev's time, 63 elements had been discovered, but scientists couldn't agree on how to arrange them in a useful way. Mendeleev wrote each element symbol on a card along with a value called atomic weight. He was determined to find a pattern which would link groups of similar elements: one group was the reactive nonmetals fluorine, chlorine, bromine and iodine; another group was the reactive metals sodium, potassium, rubidium and cesium. Mendeleev was convinced that an overall pattern existed, so he tried arranging the cards in different ways, but after three days and three nights he still hadn't found a solution. Exhausted, he fell asleep. Miraculously, as he dreamt, he began to see the pattern he'd been looking for. Mendeleev's answer was to arrange the element in columns in order of atomic weight. By doing this, groups of similar elements could be grouped in the same row, like the alkali metals and the halogens. The properties of the elements repeated in a series of periodic arrangements, so he called it the periodic table. Mendeleev was so convinced his pattern was correct that he left spaces. This was his stroke of genius. He reasoned that there was still more elements to be discovered that would fill these gaps. He even predicted the properties of these unknown elements based on their position in his table. If the table really could be used to predict the existence of elements, other scientists would have to agree that Mendeleev's ideas were right. Six years later, a new element called gallium was discovered; it's atomic weight was almost exactly the same as Mendeleev's prediction. This happened again with two other elements, filling gaps. From them, Mendeleev's table was accepted by scientists. Today the layout of the periodic table looks slightly different: while Mendeleev wrote his original table in columns, the modern table is arranged in rows. Over 60 elements were known to Mendeleev; today we know of more than a hundred, each with his own place in the periodic table, and nowadays elements are written in order of increasing atomic number, not atomic weight. The position of any element in this table allows its properties to be predicted.

                  1- Why is the figure of Dmitri Mendeleev important for chemists?

                  2- How did Mendeleev find the hidden pattern in the Periodic Table?

                  3- What problems did Mendeleev find in arranging the elements in his Periodic Table??

                  4- Why was Mendeleev's Periodic Table so important at that time?

                  5- Which are the two main differences between Mendeleev's Periodic Table and the current one?

Activity 2.3. Finally, in order to finish the lesson and evaluate the knowledge acquired in it, you should perform TASK 4 and TASK 5 so that all its sections score above 60%. You can repeat them only twice and the higher score would be considered.

 

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