Introduction
There are about 120 known chemical elements. These elements make up the many compounds that are known.
It is helpful to be able to see patterns in the chemistry of the elements. This allows us to make certain predictions about their chemistry and about the chemistry of compounds. The development of the periodic table has been the greatest step forward in our understanding of the chemistry of the chemical elements.
In this Webquest you are going to find out what is meant by the term 'element', and how John Newlands and Dmitri Mendeleev took the first important steps in developing a periodic table. Their tables had the elements arranged to show patterns in the properties of the elements.
There were obvious anomalies in both of their tables, where things didn't fit the pattern. You will be asked to find out how these anomalies were accounted for by Mendeleev.
Task
Firstly, you should find a suitable description of a chemical element. Then you will try to find out what work Newlands and then Mendeleev did to develop the periodic table. This was not easy to do in those days because there was not much information about elements (or indeed many elements) for them to base any table on. You will need to make it clear how their tables were drawn up. There were some anomalies in Mendeleev's table, which made many people ask questions about it. You will be asked to research how he explained these anomalies and how he was able to make predictions from his table.
Challenge: Try to also find out which major scientific discoveries were mainly responsible for the rapid development of the modern periodic table in which all these anomalies are resolved and explain why.
You may choose to present your findings in the form of a report or as a presentation.
Process
Step 1: Planning
The weblinks included in the 'Sources' section below will be helpful in gathering information for this task. You need to make sure you research the following:
- What is meant by the term 'chemical element'?
- What early work was done by John Newlands and Dmitri Mendeleev to develop the periodic table?
- How was Mendeleev able to explain the anomalies in his table and how was he able to make predictions from it that could be tested experimentally?
- Challenge: Which major scientific breakthroughs were responsible for the rapid development of the modern periodic table? Why?
Step 2: Research
Decide how you are going to select and order relevant information relating to the bullet points above. This will involve using the weblinks in the 'Sources' sections or using other online sources - a good place to start is BBC Bitesize. You do not need to include everything - refer back to what you are being asked to research. Do not just copy and paste sections of text which are not related.
Step 3: Preparing report/presentation
You must decide how you are going to best organise your findings within the three or four research areas. This could take the form of a report or a presentation. Remember to refer back to the research areas you need to cover.
Sources:
Description of what the term 'chemical element' means today and how it was used historically:
https://www.cs.mcgill.ca/~rwest/wikispeedia/wpcd/wp/c/Chemical_element.htm
Explanation of Newlands 'Law of Octaves'
https://chemistrygod.com/law-of-octaves
Summary of how Mendeleev developed the periodic table
https://corrosion-doctors.org/Periodic/Periodic-Mendeleev.htm
Article on the development of the periodic table, with references to the impact of other scientific breakthroughs
https://www.scientificamerican.com/article/the-evolution-of-the-periodic-system/
Evaluation
Your report or presentation should include:
- A description of what a chemical element is.
- A description of the contribution made by Newlands and Mendeleev to the development of the early periodic table.
- The explanation put forward by Mendeleev to explain away the anomalies clearly present in his table.
- Challenge: A description of the scientific breakthroughs responsible for the development of the modern periodic table.
Conclusion
You should now understand a lot more about how the early periodic table was developed. You will know about some of the scientists involved in creating it and how scientists have to be able to explain their work to others. And do you know what a chemical element is?