The complete periodic table December 23 2016, 0 Comments
Last June, the organization that officially recognizes the discovery of chemical elements and their names announced the proposed names for the final four elements on the periodic table. This governing body, the International Union of Pure and Applied Chemistry (IUPAC), took suggestions from the discoverers of the elements and then it issued the proposal. People could submit comments about the names for several months, and then in November, the IUPAC published the names. This was the final step in making them official.
The element names and atomic numbers are: nihonium (Nh) for element 113, which is named for the country of Japan; moscovium (Mc) for element 115, named for Moscow, Russia; tennessine (Ts) for element 117, named for the state of Tennessee; and oganesson (Og) for element 118, named after a Russian scientist who helped discover several elements, Yuri Oganessian. A new periodic table with these names is available at the IUPAC website, https://iupac.org/what-we-do/periodic-table-of-elements/ .
So what does this mean for the Montessori classroom? Children are ready for the abstract idea of chemical elements when they are in their elementary years. When they get an introduction to the periodic table, it should include the full set of names. Children should get a least a brief story of how elements get their names and how governing bodies of science fields bring order to science knowledge.
Children need to know, however, that there are elements that one cannot see with one’s eyes. There are quite a number of elements that are known only by the energy, particles, and atoms produced when they undergo radioactive decay.
The image below is from my newly updated card set, Discovering the Periodic Table. It comes with two sets of cards for all 118 elements, one in color and one in black and white. The card on the left is an example of the color set, and in this case sodium's symbol is color-coded red to show it is one of the alkali metals. The other card is the back of the black and white card, and it shows the type of information given for each element - physical properties, chemical properties, and other information. The front of the black and white card is like the card on the left, but with the symbol only outlined.
I updated and expanded Discovering the Periodic Table last summer after the new names were announced. At that time I added some features to help children understand the nature of the largest elements. The elements that cannot be made in visible quantities have symbols with a dotted outline rather than a solid one. The smallest of these is astatine, atomic number 85. Scientists have calculated that if one could make a piece of astatine, it would instantly vaporize itself because of the energy released by its vigorous radioactive decay.
If you tell children this, they may wonder how such an element was ever discovered. If they don’t think of it, help them arrive at this question. We want children to think about what they hear and ask about how we know what we know. The idea to search for astatine came from its place in the periodic table. Mendeleev left a blank beneath iodine on his first periodic table, implying that there was another element in the halogen family. Researchers that first identified this element used a nuclear reactor to bombard bismuth, atomic number 83, with alpha particles. This added two more protons to bismuth nuclei, and produced a small amount of astatine, which quickly decayed. Later, when researchers knew astatine’s characteristics, and they were able to find tiny traces of it in uranium ores.
After astatine, the next element that can’t be made in visible amounts is francium, atomic number 87. The dotted outline symbols don’t show up again until atomic number 101, mendelevium. It and all larger elements cannot be made in visible amounts. Researchers have made so little of elements 104-118 that the chemical properties of these elements are also unknown. In the cards with color-coded symbols from Discovering the Periodic Table, elements 104-118 have gray symbols to show that there is not enough evidence to assign them to a chemical group such the halogens.
Your children may ask if more elements can be discovered. In theory there could be, but if someone does discover more elements, it will be bigger science news than any recent element discovery. Meanwhile, help 6-9 year-olds explore the common everyday elements with the cards set, Elements Around Us from InPrint for Children. The set, Element Knowledge, will help 9-15 year-olds learn element names, symbols, and several significant groups. This set includes the first 111 elements. You can add the names and symbols of the other seven if your children are interested. They certainly won’t see those symbols in any chemical formulas.