Is hydrogen more of an alkali metal, a halogen, tetrel, or neither?

10887 Views 11 Replies 9 Participants Last post by bellisaurius, Nov 20, 2012

Sapphyreopal5

Discussion Starter · Oct 15, 2012

Pre-note: I realize now the title of this thread is not quite what I wanted it to be but I can't edit it so whatever lol. It was created when I was originally going to create this thread to see only if hydrogen should be a halogen or alkali metal only until I later on discovered the argument for classifying it as a Group 14 or 4A element :laughing:.

I was reading up on why hydrogen was placed where it is on the periodic table and I came across various yet interesting arguments suggesting hydrogen should be considered more of a halogen or even a tetrel (carbon family/Group 14 or IVA). I remember often being told that hydrogen is more of an alkali metal (although has some unique properties) and I find this information to be quite interesting. Below I created tables comparing SOME (certainly not all, as this thread would be too long!) similarities and differences between hydrogen and the different groups it could be classified as/grouped with (is currently an ongoing debate).

What are your thoughts? Should hydrogen be considered more of an alkali metal, a halogen, a tetrel (carbon group), or considered classless (or in other words, its own class)?

A. Hydrogen is more of an alkali metal (is placed above lithium on periodic table)
http://www.colorado.edu/physics/2000/periodic_table/atomic_structure2.html#alkali(one website stating why hydrogen should be more classified as an alkali metal)
SOME of the similarities and differences between hydrogen and the alkali metals:

Hydrogen and alkali metals alike	Hydrogen and alkali metals different
Have 1 electron in valence shell	Hydrogen can either gain or lose an electron during reactions, whereas alkali metals only lose electrons during reactions
Hydrogen can lose an electron in reactions, like alkali metals	Alkali metals can only form ionic compounds, whereas hydrogen can create both ionic and covalent compounds
Valence shell configuration is Ns[SUP]1[/SUP]	Hydrogen is a gas at room temperature, whereas the alkali metals are solid at room temperature
Can form halides	Hydrogen can be an oxidizing or a reducing agent, whereas alkali metals can only be reducting agents
Are good "reducing agents" (hydrogen a reducing agent when combined with nonmetals)	Hydrogen's first ionization energy is much higher than the alkali metals (Hydrogen at about 1314 kJ/mol, Lithium [has highest first ionization energy of the akali metals] at about 520 kJ/mol)

http://www.nature.com/nature/journal/v393/n6680/abs/393046a0.html (website discussing hydrogen [not] becoming an alkali metal under extremely high pressure [such as when placed on Jupiter], despite calculations suggesting otherwise)

B. Hydrogen is more of a halogen (is placed above fluorine on periodic table)
http://hydrogentwo.com/hydrogen-halogen.html(one website stating why hydrogen should be more classified as a halogen)
SOME of the similarities and differences between hydrogen and halogens:

Hydrogen and Halogens Alike	Hydrogen and Halogens Different
Hydrogen can gain an electron in reactions, as halogens do in reactions.	Hydrogen has 1 electron in valence shell and halogens 7.
Both act as negative ions when bonding with metals.	Hydrogen can either gain or lose 1 electron, halogens can only gain 1 electron.
Hydrogen and halogens both are non-metals.	Halogens can have a large atomic radius, whereas hydrogen has a very small atomic radius.
Molecules of both are diatomic (A[SUB]2[/SUB]).	Halogens have a valence electron configuration of Ns[SUP]n[/SUP], whereas hydrogen has an electron configuration of 1s[SUP]1[/SUP].
Both can form both ionic bonds and covalent bonds.	Hydrogen ions are unstable in water, whereas halogen ions are stable in water.

http://www.google.com/imgres?
um=1&hl=en&sa=N&biw=1366&bih=681&authuser=0&tbm=isch&tbnid=dFd1CV_qpdf6YM:&imgrefurl=http://www.answers.com/topic/periodic-table&docid=PF_X0JzAEfdnuM&imgurl=http://content.answcdn.com/main/content/img/McGrawHill/Encyclopedia/images/CE498900FG0010.gif&w=640&h=352&ei=UEh7UKfxDYrg8ATJsYGwBw&zoom=1&iact=hc&vpx=647&vpy=282&dur=605&hovh=166&hovw=303&tx=155&ty=119&sig=112432762932647133545&page=2&tbnh=136&tbnw=248&start=15&ndsp=25&ved=1t:429,r:7,s:20,i:224(periodic table where hydrogen is grouped with the halogens)

http://onlinelibrary.wiley.com/doi/10.1002/open.201100015/full (this article discusses how hydrogen and halogen bonds are similar and different from each other)

C. Hydrogen should be considered more of a tetrel (is placed above carbon on the periodic table)
http://www.reed.edu/reed_magazine/summer2009/columns/noaa/downloads/CronynHydrogen.pdf(one document that states why hydrogen is more of a tetrel [carbon group]).
SOME of the similarities between hydrogen and the tetrel family, primarily carbon and silicone:

Hydrogen and Tetrels (primarily C and Si) Alike	Hydrogen and Tetrels Different
Valence shells are half-filled (hydrogen = 1 out of 2, tetrels= 4 out of 8).	Hydrogen is gas at room temperature, whereas Group IVA/Group 14 elements are solid at room temperature.
Electronegativity values are comparable (Hydrogen 2.1, Carbon 2.5, Si 1.8, etc.)*.	Hydrogen's valence electron configuration is 1s[SUP]1[/SUP], whereas the tetrels have a valence electron configuration of ns[SUP]2[/SUP]np[SUP]2[/SUP].
First ionization energy values are similar (Hydrogen at about 1314 kJ/mol, Carbon at about 1.088 kJ/mol)*.	Hydrogen is monovalent (1 valence electron), whereas the tetrels are tetravalent (4 valence electrons).
Hydrogen and the tetrels can form covalent bonds.	Hydrogen can form both ionic and covalent bonds, whereas the tetrels can form only covalent bonds.
Hydrogen and the tetrels (primarily Hydrogen and Carbon) have similar electron affinities (forming non-polar covalent bonds).	Various tetrels can come in the form of allotropes (carbon [ex. graphite, diamonds], silicone [amorphous, crystalline]) whereas hydrogen does not.

*values will differ source to source. I got these values from my textbook.
Hein, Morris, and Susan Arena. Foundations of College Chemistry. 13th ed. Hoboken, NJ: Wiley;, 2011. Print.

D. None of the above/Hydrogen should be considered its own unique group (has its own spot on the periodic table on periodic tables)
http://www.citycollegiate.com/positionofh.htm (one website that states why hydrogen should have its own place on the periodic table)

http://www.friendsmania.net/forum/2nd-year-chemistry-notes/25788.htm (one person's notes on hydrogen's similarities and dissimilarities with the mentioned groups above that I thought were worthy of mentioning)

Reasons why hydrogen is considered unique:

The most common isotope of hydrogen (protium) has only 1 proton and 1 electron, meaning it has no neutrons. Every other element has neutrons (not counting isotopes that are unstable).
It can gain (more frequent) or lose electrons in reactions. Every other element either gains, loses, or shares electrons.
It shares similar properties with multiple groups of the periodic table, as discussed above (thus is hard to classify under a specific, unlike other elements!).
Due to its high re-activity, hydrogen can bond with almost all of the elements.
Hydrogen is said to be the first element ever created, according to the Big Bang Theory.

http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel_pre_2011/patterns/groupsrev1.shtml(periodic table with hydrogen in its own spot)

More information:
http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Descriptive_Chemistry/Main_Group_Elements/Group__1%3a_The_Alkali_Metals/Chemistry_of_Hydrogen(some basic hydrogen facts)

http://www.oup.com/uk/orc/bin/9780199236176/ch10.pdf(some information on hydrogen's unique chemistry)

https://fcserver.nvnet.org/~tisosky/FOV1-0004CBC5/FOV1-0005FB31/electronegativity_table_bw.jpg(Electronegativity periodic table chart)

http://www.vias.org/genchem/covbonds_12584_03.html (Information on compounds containing carbon and hydrogen [hydrocarbons]).

http://www.austincc.edu/emeyerth/polarity.html(information about ionic, polar covalent, and non-polar covalent bonds and a little about electron affinity).

http://aether.lbl.gov/www/tour/elements/stellar/stellar_a.html (information about formation of high mass elements and what happens inside of a star. Also talks about hydrogen being thought of as being the first element ever created according to the Big Bang Theory).

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bellisaurius

· #12 · Nov 20, 2012

The periodic table is just something that makes properties easy to understand/memorize. So, what's going on here is partly an imaging problem, because as you noted, the most common periodic table dumps hydrogen above group I.

Alternatives exist that recticfy some of these issues. I think this one is useful to your current idea:

Although this one has its merits too

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Should hydrogen be classified as an alkali metal, a halogen, a tetrel , or none?

Alkali Metal

Halogen

Tetrel (Carbon Group)

None of the above; should be considered its own group

Is hydrogen more of an alkali metal, a halogen, tetrel, or neither?

Sapphyreopal5

bellisaurius

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