The longest alphabetical sequence in the periodic table

Here's an interesting question:

What's the longest alphabetical sequence in the periodic table?

I suppose it's important to first clarify what alphabetical order in terms of the table means. Thankfully, each element is denoted by either one or two letters, so it's not a complicated process. I will consider the elements with one letter to take precedence in any alphabetical ranking. 

Almost off the bat, there's a strong three element sequence with hydrogen (H), helium (He), and lithium (Li). Unfortunately, beryllium (Be) ruins it - so three is the number to beat.

Immediately, we surpass it, with:

• Boron (B)
• Carbon (C)
• Nitrogen (N)
• Oxygen (O)

This is also probably the longest sequence consisting of elements we interact with on a daily basis. 99% of the air is covered by the latter three elements, and (especially) carbon, nitrogen and oxygen are fundamental elements to organic chemistry. Fluorine (F) sadly makes the sequence shorter than it would otherwise be. So four is the number to beat, and it takes a while to do so.

Calcium to vanadium consists of four elements, too; however, the longest sequence comes not long after - six elements, or:

• Bromine (Br)
• Krypton (Kr)
• Rubidium (Rb)
• Strontium (Sr)
• Yttrium (Y)
• Zirconium (Zr)

I find this particular sequence especially fascinating, as it manages to include two of the lowest ranking elements alphabetically - only zinc is below yttrium or zirconium. 

We nearly get another six, from silver (Ag) to tellurium (Te), if only tin (Sn) and antimony (Sb) were swapped around. There is, however, one final six, found deep amongst the actinides:

• Berkelium (Bk)
• Californium (Cf)
• Einsteinium (Es)
• Fermium (Fm)
• Mendelevium (Md)
• Nobelium (No)

So the answer to the question is six. 

Now, I could leave the blogpost there, since I've answered the question, but what I've written so far feels a bit low effort because all I've done is use my reading skills to look at a periodic table - anyone could have done that. So instead I'll talk more in depth about one of the sequences, and since all of the actinides are very radioactive, have short half-lives, and are more curiosities than practical, I'll discuss the Br-Zr route. However, it won't be in depth as I usually do when discussing elements, not least as some of them likely deserve their own posts:

• Bromine

The third of the halogens, and one of only two elements - the other mercury - which is liquid at room temperature. Most of our industrial bromine is sourced from the oceans, and historically it was added to leaded fuel to stop the lead from depositing in engines. However, bromine is more commonly used today in fire retardants, hand sanitisers, and bleaching. It can also prove deadly if inhaled.

Bromine water is also an effective way of testing for certain functional groups, such as alkenes and phenols; in the case of the latter, it opens up the C=C double bond, and in the case of the former, 2,4,6-tribromophenol forms, which produces a white precipitate.

• Krypton

As with all the noble gases, krypton is an inert gas which doesn't do much. It's present in various lightbulbs and was once used to help define the value of the metre, by passing light through a krypton discharge tube and measuring its wavelength before upscaling it by 1,650,763.73.

Krypton may be inert, but experiments saw it react with fluorine to produce KrF₂, often at extreme conditions (this 1963 paper describes it forming at -150℃, and only being stable up to -30℃).

• Rubidium

Wrapping our way round a period, we end up at the second most reactive metal, rubidium. When it reacts with water, it gets quite explosive; in air, it spontaneously ignites. It's thus probably not surprising that all the images I've found of it see it sealed up in a vial.

Rubidium isn't particularly useful commercially for these reasons. It's always found with caesium in nature, though at least its more reactive cousin gets to be used as part of the definition of a second. It's also rarely the subject of a blogpost.

• Strontium

The only element named for a British location, strontium is in Group 2, and thus has similar properties to elements like calcium. One of its isotopes, ⁹⁰Sr, is the chief risk of nuclear fallout - it forms during the process of nuclear decay, and since it acts similarly to calcium, can accumulate in one's bones if ingested - this can cause cancer. Otherwise, strontium is rather safe and non-toxic, and is used in the production of magnets and fireworks; it was also a component in televisions when cathode ray tubes were how images were displayed on screens.

• Yttrium and zirconium

These last two elements are both transition metals. Yttrium is one of four elements named for the small Swedish town of Ytterby, and is used in ceramics, hosting red phosphors in lamps, and televisions, often in the form of yttrium aluminium garnet - this being a crystal containing yttrium, aluminium, and oxygen (Y₃Al₅O₁₂) - which is then doped with various rare earth metals.

 

 

Zirconium, meanwhile, is mostly used in nuclear power stations as it doesn't absorb neutrons; it is also used through zirconium oxide (ZrO₂) to make ceramics such as crucibles, bricks, and ceramic knives. Zirconium is also present in jewellery through zircon (ZrSiO₄) and can be cut into gemstones, and other uses of zirconium include getters - materials that maintain vacuums - and corrosive agents, as it is quite resistant to various acids and alkalis.

 

 

 

Image sources:

Bromine: https://images-of-elements.com/bromine.php

Krypton: https://images-of-elements.com/krypton.php

Rubidium: https://en.wikipedia.org/wiki/File:Rb5.JPG

Strontium: https://en.wikipedia.org/wiki/File:Strontium_destilled_crystals.jpg

Yttrium: https://images-of-elements.com/yttrium.php

Zirconium: https://en.wikipedia.org/wiki/File:Zirconium_crystal_bar_and_1cm3_cube.jpg