Unwrapping the periodic table
Niki Kaiser, chemistry teacher and research lead at Notre Dame High School in Norwich, speaks to us about the wonder of the periodic table, and her experiences of sharing that wonder with her students.
As I’m writing this, I’m drinking coffee from my periodic table mug. This mug often prompts questions from my children (Who’s the man with the beard? What’s Na?), so it’s something they’ve grown up with.
For me though, my earliest memory of the periodic table is probably seeing it on the back wall of the chemistry lab at my school in Hastings, with Mr Smith as my chemistry teacher. It took me a long time to work out what it was and what it was for. It started out as just a series of letters, and then some of those letters started to mean something, and only later did I start to appreciate the puzzle and the structure behind it.
As a teacher, I have the opportunity to see children come in with only a vague awareness of its existence, and then slowly unwrap the meaning and the wonder of it. There are a lot of 'wow' moments when you teach the periodic table.
The first is when you say that this table contains everything in the universe, as far as we know – that’s a phenomenal concept. Then at the same time you’ve got the variety of the elements in it. The Tom Lehrer song that lists all the elements really captures that variety.
And finally you’ve got the language side of it – the fact that these symbols are used all over the world. My husband is German and he’s a chemist, so he grew up with exactly the same element symbols. They're called different things, but the symbols are the same. For a lot of children it’s a revelation when they suddenly understand that the table is used universally.
The first time I use the periodic table in teaching is often when I’m moving on from the idea that everything is made up of atoms or particles, to actually starting to name them. Introducing the periodic table is a way of saying, "This is our language, this is where we start, this is what we build things from."
To begin with it’s important just to increase familiarity. We can use the periodic table as a starting point for understanding things we talk about all the time, and to identify the more common elements like carbon and oxygen.
By the time students reach secondary school – which is the level I teach at – they will have heard of CO2 and H2O and O2, but they might not have made the connection between these concepts they hear every day and the elements in the periodic table.
That’s why to start with we focus mainly on the gross structure – the metals are here, the non-metals are there, and so on. Once they have grasped this, you can start to show that there’s some order to it. We talk about the Group 1 alkali metals and start to see that they’re all similar in some way. Then at the other extreme there are the gases and halogens. The idea that the table shows us how to group similar elements starts to come together in this way.
As we dig down further, the pattern and the structure begin to reveal themselves a bit more. There’s often an "ah" moment when students realise how the number of electrons in the outer shell relates to the group number.
It never fails to surprise me how people do appreciate the wonder of it. There’s another "ah" moment at A-level when you introduce orbitals, and suddenly students understand why there’s a p-block or an s-block.
Imagine being at the start of this journey, where you've got to come up with that structure from nothing.
We also teach the story of how the periodic table came into being, and we learn about Mendeleev and others who contributed to its development. I say to the children: "From the moment that you walk into the lab you have a structure there on the wall. These elements are grouped together in this way and that’s your starting point. Now imagine being at the start of this journey, where you’ve got to come up with that structure from nothing."
That journey of discovery is one that the students can take for themselves. Even though the periodic table has been created already, they get to almost rebuild it themselves as they go through and learn about the groupings – first separating into metals and non-metals, then the different groups, then the orbitals and the different blocks.
The way we teach it, you’re unwrapping the periodic table layer by layer. It starts off as a thing that contains everything and then you realise there are different layers to it and you gradually delve deeper. It’s similar to when you teach the atom – you start off with particles, then atoms, then electron shells and so on.
I think it’s important when teaching the periodic table not to lose the wonder of it. Even though we don’t have to start from scratch as Mendeleev and his contemporaries did, we can still appreciate what a wonderful amazing structure it is. Even if you’re not telling the story of the octaves and of Mendeleev, it’s good to keep that story in the back of your mind.
The periodic table really is the language of chemists. Chemistry, as a subject, can feel quite tricky to students, because we have to knit together three conceptual levels: the sub-microscopic, the macroscopic and the symbolic. The key is to understand that the symbols aren't just another hurdle we have to jump through, they're something that can help us represent complex ideas. And that’s really amazing.
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