Teaching / Learning

ChroMolyTung – The Seaborgium Monster of Group Six

[TL;DR – show me the periodic table mnemonics]

Mnemonics. Phrases, acronyms and other associations we all used as children to help remember the order of the planets or the colours of the rainbow. But are there similar methods to help remember facts and figures in chemistry? Yes indeed! A quick Google search reveals independent websites as well as a Wikipedia entry on the things. Among the pages of J. Chem. Educ. you can find tricks to remember the α,ω-dicarboxylic acids (see below), thermodynamic variables, the Krebs cycle, the base SI unitsZ and E nomenclature and many more. But do any of these actually help you learn anything?

Oh My Such Good Apple Pie, Sweet As Sugar

(oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic, sebacic acid)

In 1992, Battino wrote a ‘Provocative Opinion’ piece about how rote learning has a useful role in the teaching of Chemistry. In it he makes the point that knowing the names of functional groups and molecules (easily accomplished by rote) is critical for us to communicate with each other about our subject. By learning definitions, periodic trends such as electronegativity, how to balance chemical equations, or how to convert [H+] = 1 x 10¯into pH = 4, we form a foundation upon which connections between concepts and a deeper understanding of say, thermodynamics, or chemical reactivity, can be built. Furthermore, there is a lot that can be done with simple facts. You may not yet know much quantum mechanics (for example), but can still propose that a metal hydroxide and hydrogen are the products of a reaction between an alkaline metal and water.

A different article, written in 1945 by Flipper and Morris, takes a similar view. On mnemonics, they add:

Students who employ mnemonic devices should exercise
care in selection of key words lest the device be more difficult to remember than the material it is intended to represent.

This is never more true than with periodic table mnemonics. A good example of an outrageous series is the nonsense phrase Motcru rh’p’d agcd in Sn’sb’ to ‘help remember’ elements 42 to 51. For a recent commentary on the merits (or lack thereof) of memorizing the periodic table, check out this 2015 post from Chemjobber.

Adopting the point of view that this is something useful to learn, I thought it would be interesting to try my hand at some new periodic table mnemonics. These would differ from previous attempts in two respects. Firstly, most chemistry mnemonics, including those for the periodic table, seem to bear absolutely no relation to the information you are trying to remember. What does apple pie have to do with α,ω-dicarboxylic acids, and what does an oil rig have to do with electron transfer? I feel this disconnect makes the mnemonic, and so also the subject matter, more difficult to remember in the long-term. I wanted to make linked mnemonics. Secondly, most (if not all) d-block mnemonics are period-based, rather than group-based. Yet when I’m sat in a lecture, and the speaker starts talking about a particular transition metal, I want to quickly remember which group that element is in so I can calculate the d-electron count, if it is an early/late transition metal, etc. For me, a group-based mnemonic system was going to be more useful than a period-based one.

So…below you can check out my first attempt at a system of linked, group-based mnemonics for the d-block. It was actually quite fun putting them all together, in the end. In each case I use the number of the group to inspire a theme for the mnemonic (the link). Group 6 has a nautical theme (6 = sexi- = sextant), group 10 is currency (10 = decimal system used for money), and group 11 is sports (11 = number of players on a football/soccer team). To recall the elements for a given group, I use the number to trigger the theme, which in turn triggers the mnemonic. For example, group 6 triggers ‘sextant’ (nautical theme), which triggers my remembered phrase “ChroMolyTung, the Seaborgium monster of Group 6”. Thus the four elements Chromium, Molybdenum, Tungsten and Seaborgium are memorized (in order), using a mnemonic associated with the number 6 = Group 6.

Some mnemonics in my system clearly work better than others, and I will no doubt find them easier to remember because I spent time working them out. One immediate problem is that some of the mnemonics give the element order from the top to the bottom of the group, and others vice versa. However, the 3rd row metals are typically more familiar than those of the 6th, so it’s fairly easy to orient yourself. In general, if you like the concept but something isn’t clicking, why not work out an alternative? Just make sure the group number is somehow linked to the mnemonic. And please do let everyone know your new mnemonic in the comments!

Group 3 (Sc, Y)

Tri. ‘Tri-‘ is a prefix meaning three (e.g. a triangle is a shape with three angles). Tri rhymes with sky. Sky = Sc + Y (Scandium + Yttrium).

Group 4 (Ti, Zr, Hf, Rf)

Square. There are four sides to a square. ‘Squaring up’ to someone is getting ready for a fight. If you’re going to be a teaser (TiZr, ‘Ti’tanium-‘Zir’conium), you might have (‘Haf’nium, Hf) to get rough (‘Ruth’erfordium, Rf).

Group 5 (V, Nb, Ta, Db)

Senses. There are five traditional senses: hearing, smell, sight, touch and taste. Dubstep (‘Dub’nium, Db) is a genre of music you listen to (hearing). Smells are often described as tantalising (‘Tant’alum, Ta). In the 1999 film, Neo (‘Nio’buim, Nb) defeats his enemies by ‘seeing’ in the Matrix (sight). The two remaining senses both start with T, an Audi ‘TT’ is a vehicle, and so is a van (‘Van’adium, V).

To help remember the order of this group you can string together a short story. For example… After a night out ‘listening’ to dubstep, you get drawn into a fast food joint by a tantalizing ‘smell’ – only to be attacked by Agent Smith! You put up a good fight as you can ‘see’ in the matrix like Neo, before making a quick getaway in your Audi ‘TT’/vehicle/van.

[Note – this kind of storytelling/visualization mnemonic is inspired by the memory techniques described in You Can Have  An Amazing Memory by Dominic O’Brien]

Group 6 (Cr, Mo, W, Sg)

Sextant. A sextant is an instrument used by sailors to navigate at sea using the stars, it has a graduated arc of sixty degrees. Using a little imagination, ‘ChroMolyTung‘ (‘Chro’mium, Cr; ‘Moly’bdenum, Mo; ‘Tung’sten, W), becomes the Seaborgium (‘Sea’borgium, Sg) monster of group VI.

Group 7 (Mn, Tc, Re, Bh)

Musical notes. There are seven notes in the western diatonic scale (A-G). I always found playing guitar to be great fun, but the music theory less so. Man (‘Man’ganese, Mn), technically (‘Tech’netium, Tc) you are rheally (‘Rhe’nium, Re) bohring (‘Bohr’ium, Bh).

Group 8 (Fe, Ru, Os, Hs)

Pieces of Eight.Pieces of Eight‘ have fictional associations with pirates. I imagine a pirate ship occupied by four characters, positioned from the sky to the sea (top to bottom of the group). Iron Man (Iron, Fe) sits in the crow’s nest (he flew there), Rufio (leader of the Lost Boys – Ruthenium, Ru) steers the ship on deck (he just captured the vessel from Captain Hook), the Wizard of Oz (Osmium, Os) hides below deck (like in the film but behind a curtain), and David Hasselhoff (Hassium, Hs) plays lifeguard amongst the waves.

Group 9 (Co, Rh, Ir, Mt)

999/911. If you dial 999/911, you might (Meitnerium, Mt) get rid (I’rid’ium, Ir) of rhobbers (‘Rho’dium, Rh) using cops (‘Co’balt, Co).

Group 10 (Ni, Pd, Pt, Ds)

Currency. Ten is the base of the decimal system, which we use (amongst many things) for money. A nickel (‘Nickel’, Ni) is 5 cents, or 5 pennies. In the decimal system, to make ten we must times by two (so 2 x P). The two P’s of the d-block are Palladium, Pd and Platinum, Pt (ordered down the group alphabetically). After pennies and nickels come dimes (Darmstadtium, Ds).

Group 11 (Cu, Ag, Au, Rg)

Sports. Eleven is the number of players on any football/soccer team (also cricket, field hockey…). In sports, prizes for coming 3rd, 2nd and 1st are typically awarded with bronze (the main constituent of which is Copper, Cu), silver (Silver, Ag) or gold (Gold, Au) medals, respectively. Alongside football, another popular sport is rubgy (Roentgenium, Rg).

Group 12 (Zn, Cd, Hg, Cn)

Zodiac/Hurricanes. There are twelve signs in the Western zodiac, and force twelve on the Beaufort wind force scale corresponds to the maximum wind speed of a hurricane. The zodiac is a celestial coordinate system, and the only d-elements with celestial names are Copernicium, Cn and Mercury, Hg. (The planet Mercury is also the fastest planet to orbit the sun – a planetary hurricane!) Golf is a game you would not want to play in strong winds, so grab your caddy (Cadmium, Cd) and get your galvanized (Zinc, Zn) steel clubs outta there!

These d-block mnemonics can even be summarized in picture-form…

Periodic Table

(in case you can’t make it out, that’s a ‘teaser trailer’/Ti-Zr trailer, a fist for ‘might’/Meitnerium, a waste bin for ‘get rid’/Iridium, and facial expressions for ‘really?!’/Rhenium and ‘boring’/Bohrium)

Happy memorizing!

Practical Tips & Tricks

Unusual Lab Techniques: Radial Chromatography

I love hearing about/testing unusual laboratory techniques. Just because you or your colleagues have always done something a certain way, doesn’t mean there isn’t a faster, more effective, or cheaper process available. You also never know when all conventional methods to achieve something will fail (typically when attempting to purify some badass new compound), and you need to dig a little deeper into the tool box… So in case you didn’t hear about this one yet, here I’m highlighting radial chromatography (also known as centrifugal chromatography or centrifugal thin layer chromatography).

Many readers will be all too familiar with column chromatography, frequently used in synthetic chemistry to separate and purify materials. Here, solvent (the mobile phase) is eluted through silica or alumina (the stationary phase) using gravity or applied pressure (see also flash chromatography). You add your crude product mixture on top of the stationary phase, and the various components elute through the column at different speeds. The separated (hopefully now pure!) materials are then collected as they elute out the bottom.

Column chromatography sequence
conventional column chromatography

In radial chromatography, solvent is instead eluted using centrifugal force. A circular plate containing a thin layer of silica/alumina is spun at high RPM, with crude material and solvent added in the centre. Continued rotation and addition of solvent separates out the individual components into rings. Eventually these reach the edge of the plate whereby the solution flys off into a specially designed enclosure, runs down the sides, and is collected as per the conventional approach. Using coloured compounds the process is actually rather pretty, as shown in the video below (check it out at ∼2 min).

There are at least two commercially available models (the Chromatotron and the Cyclograph), and apparently they can be made on the cheap from repurposed unused equipment. A fairly recent study in J. Chem. Educ. reports the use of a Chromatotron in undergraduate experiments for the separation of nitroaniline isomers.

Sadly I have never worked in a lab that had one, and only heard of the technique from reading a 2001 Lanny Liebeskind paper. If anyone has ever used these in their research I’d love to know – how do they compare to conventional column chromatography? Can they compete in any way with modern automated flash chromatography systems, such as those offered by Biotage or ISCO?