Lesson plan: KS3 chemistry – the periodic table
Bring creativity into your chemistry lab with Dr Joanna Rhodes’ fascinating ideas for exploring the periodic table
Inspired by the recent discovery of new elements in the periodic table, this lesson will help your students to learn about how elements have historically been named and the current IUPAC rules for naming our most recent additions to the table. Armed with this contextual information students will attempt to create their own element names. In the main activities students investigate the properties of elements and deduce their relative positions in the periodic table. Can you, like Mendeleev, predict the properties a ‘missing element’ would have? Finally, students are invited to speculate on whether we have reached the end of the periodic table and what would happen if any heavier elements were found in a so-called ‘Island of Stability’.
WHY TEACH THIS?
The chemical elements are the heart of chemistry and the building blocks of the universe. When we make and discover new synthetic elements we are carrying out chemistry of the type only seen naturally in the stars. Use this lesson to capture students’ imagination, drawing on the recent confirmation that four new elements will be added to the periodic table.
The Name Game
The names of chemical elements have huge historical significance. Many derive from ancient Latin or Greek and more recently have been named after significant modern scientists and places. Students often find fascinating the small number of elements whose symbol does not match the letters in its modern name.
Why is potassium K? Why is lead Pb? Using a periodic table, ask students to identify all the elements that have a different symbol to the letters in its name. Then divide into groups to use computers or tablets to identify the origins of the symbols and the elements’ alternative names. Now introduce the discovery of the latest new elements with a video such as this interesting one from Professor Sir Martyn Poliakoff [AR1]. Students are usually amused when I explain how the placeholder naming system works, giggling audibly when I tell them that Ununpentium (the placeholder for element 115) simply means ‘one one five-ium’. Stretch your more able students by asking them what the placeholder names for 105, 116 and 120 might be.
Now explain to students that the IUPAC rules allow an element to be named after a mythological concept, a mineral, a place or country, a property, or a scientist. Working in small groups, ask students to come up with their own name for one of the newest elements. They must be able to explain the significance and meaning behind their suggestion and it must meet the IUPAC rules. Students could vote on the shortlist of favourites to win a prize.
Show students the beautiful element cartoons created by Kacie-D [AR4]. Each element is anthropomorphised into a stunning representation of its properties as a character. Ask students to create their own element artwork by researching the properties and uses of their chosen element and creating a design around this. If you coordinate the class you could recreate a section of the periodic table in your laboratory, or even coordinate a number of classes to create your school’s very own artistic version of the periodic table.
The elements are entrenched in popular culture where it is much easier to create a new element than it is in real life. Examples of fictional elements include Unobtainium (Avatar), Kryptonite (Superman), Mithril (Lord of the Rings), Adamantium (Greek Mythology and X-Men) and Divinium (Call of Duty) . Ask students to create, name and describe their own fictional heavy element. As we know, the properties of elements follow a trend as you go down the group, alkali metals becoming more and more reactive for example. The noble gases have steadily increasing melting points. One of my favourite fictional elements, created by a student, took advantage of this property to create elixirium, a noble element but liquid at 10°C with a brilliant blue sheen. This completely unreactive cold liquid could be poured over injuries to prevent infection and bacteria and enabled healing within hours!
1 – Practical Properties
Begin this section by demonstrating the similar properties of elements in the same group, using the alkali metals. You could carry out the experiments showing how the metals react with air and water, or show an accurate video [AR2]. This will demonstrate what it means for elements to have similar properties as all the alkali metals react quickly with air, oxidizing and appearing to go dull, all are soft enough to be cut by a knife and all react violently with water. The aim of the student activity that follows is for them to identify experimentally, from a selection of substances, which two of those are elements that belong within group 2 of the periodic table. Students are told:
1) Elements within group 2 are metals
2) Elements within group 2 react with hydrochloric acid by fizzing and giving off hydrogen gas.
Provide students with test tubes and test tube racks, 0.1M hydrochloric acid, dropping pipettes and spills (to light in order use the squeaky pop test for hydrogen gas). The Group 2 elements you should use are magnesium and calcium. Other elements that you could include, for students to eliminate from their deductions, are copper, aluminum foil, carbon, sulfur and silver wire.
2 – Mendeleev’s Missing Elements
When Mendeleev compiled the periodic table he had only the mass number to provide an approximate order, rather than atomic number, which came later with the discovery of protons, neutrons and electrons. The problem, if you arrange the elements strictly in order of atomic mass, is that some elements end up grouped with elements that have different properties; they are in the wrong place. Mendeleev was certain that each group (column) in the periodic table must contain elements that share properties, just like the ones your students have discovered, and so he left gaps for elements that had not yet been discovered.
To illustrate this, use an ordinary pack of playing cards, shuffle the cards and hand each student a single card. You will be left with a number of ‘undiscovered’ playing cards. The task for students is to cooperate with each other to suggest which playing cards remain to be discovered. Students will usually arrange the playing cards they have by suit, then in order of number. Support students if they seem to be going in the wrong direction by explaining that the suit is the ‘property’ of the card. All cards with the same ‘property’ lie in the same group and by increasing number, just like elements in the periodic table. Very soon the missing cards will be identified and you can carry out a big reveal (for example by keeping the cards in a sealed envelope until the end of the activity). This is no magic card trick but students are always delighted to see the cards they identified in the envelope. It also simplifies the process that Mendeleev went through to predict as yet undiscovered elements.
Assessment for Learning
Create a copy of the periodic table with some elements missing, but which is otherwise standard. It would be to easy to ask students to identify the missing elements, something they can do by checking the periodic table on the wall in the classroom. However, the point of this exercise is to predict the elements’ properties. Place ‘property cards’ around the classroom for other elements that remain on your altered version of the periodic table. Students should visit these, making notes on the properties of these elements. This allows them to build up a picture of the properties of a group. For example, group 0 contains the noble gases, which are unreactive and have very low melting points. Ask students to write a summary of the expected properties of the elements that are missing. You can make the activity competitive by awarding points for each property that they deduce that appears on your own element property card for the missing element.
STRETCH THEM FURTHER
The island of stability
Elements that have been created synthetically in the laboratory are typically short lived. Their nuclei are not stable and they radioactively decay very quickly back into other lighter elements like the ones from which they were formed. Richard Feynman predicted that if enough neutrons could be incorporated into the nucleus then the ratio of nucleons could create stable isotopes of even heavier elements, a so called Island of Stability for supermassive elements [AR3]. Perhaps these elements could be produced in sufficient quantities to test chemically or even use as new materials. Download ‘Nuclear’, an App by Escape Velocity Limited. This app is a beautifully rendered model of the atom that allows you to build each element in the periodic table by adding protons, neutrons and electrons. The aim is to let you learn about each of the elements of the periodic table by constructing a stable version of that element. Once a stable element has been created it is unlocked in the periodic table. Can any of your students unlock and create them all?
[AR1] INTRODUCING THE NEW ELEMENTS OW.LY/XNARD
[AR2] THE REACTIONS OF THE ALKALI METALS OW.LY/XNAWN
[AR3] THE ISLAND OF STABILITY – DISCOVERY NEWS OW.LY/XNB0O
[AR4] ELEMENT CARTOONS OW.LY/XNB4C
[AR5] FICTIONAL ELEMENTS OW.LY/XNB8V
ABOUT OUR EXPERT
Dr Joanna L. Rhodes M.Chem, D.Phil, MRSC is a teacher of science at Shelley College, Huddersfield.