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

  • Alkali Metal

    Votes: 1 4.8%
  • Halogen

    Votes: 1 4.8%
  • Tetrel (Carbon Group)

    Votes: 1 4.8%
  • None of the above; should be considered its own group

    Votes: 18 85.7%
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Discussion Starter #1
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 alikeHydrogen and alkali metals different
Have 1 electron in valence shellHydrogen 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 metalsAlkali 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 halidesHydrogen 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 AlikeHydrogen 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) AlikeHydrogen 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:

  1. 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).
  2. It can gain (more frequent) or lose electrons in reactions. Every other element either gains, loses, or shares electrons.
  3. 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!).
  4. Due to its high re-activity, hydrogen can bond with almost all of the elements.
  5. 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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:laughing:

Hydrogen is neither, Hydrogen is in a class of its own. In fact I believe that Frank Sinatra wrote a song dentitled "My way", that was actually dedicated to Hydrogen. :tongue:

All the chemical properties arise from the quantum mechanics involved, the periodic table is the way in which we try to make sense of these trends. I would say that the properties of Hydrogen is quite unique.

Also, did you know that most elements have been shown to have metallic electronic states at very high pressures, where the energy gap between the valence band and the conduction band closes. Metallic hydrogen is said to exist at the centre of very dense gas planets. Metallic oxygen exists in stars and hence astronomers refer to the presence of oxygen and heavier elements relating to the level of "metallicity" of stars.
 

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Also, did you know that most elements have been shown to have metallic electronic states at very high pressures, where the energy gap between the valence band and the conduction band closes. Metallic hydrogen is said to exist at the centre of very dense gas planets. Metallic oxygen exists in stars and hence astronomers refer to the presence of oxygen and heavier elements relating to the level of "metallicity" of stars.
I wondered why cosmologists referred to anything heavier than helium as metallic. I thought it was to do with the fact that at the beginning of the Universe everything was only Hydrogen or Helium, some trace amounts of Lithium. After Helium, the first elements are metals, Lithium and Beryllium, and so the elements immediately after Helium are metallic, Boron is semi-metal and carbon does all sorts of weird crap that makes it have similar properties to metals.

Hydrogen has no full Electron shells (every other atom does) so I think this in itself gives it properties inherent in no other part of the periodic table. The majority of chemistry is the study of electrons, Niels Bohr's study on the quantum state of electrons i.e. Electrons form shells, and only so many electrons can share the same shell lies at the heart of Chemistry today. Chemical properties come as a result of what electrons lie in the outermost shell, it's because of this Hydrogen is unique: where as other elements have fill 8 different types of outer shells, Hydrogen only has space in it's electron orbit for 2 electrons before the shell is filled.

I'm making a presumption here feel free to correct me, but it's like alkalis because it's only got 1 electron to empty it's shell, it's like halogens because it only needs 1 electron to fill it's shell, and it's like carbon because it's halfway between having either emptied it's outer shell or filled it's outer shell.
 

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I tried looking up definitions of "alkali metal", "halogen" and "tetrel" - but they were not helpful, they just listed the elements in the group lol

I would not mind Hydrogen being considered part of several groups (I don't see why it can not).

Looking at the different column with alkali metals and with halogens ... its biggest differences seems to be from only having on electron shell (which is a big enough difference, but only helium shares that trait ... a few others do as well after they lose an electron)
 

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)

Halogens can have a large atomic radius, whereas hydrogen has a very small atomic radius.

Halogens have a valence electron configuration of Nsn, whereas hydrogen has an electron configuration of 1s1


Although being able to gain and lose an electron is a significant note, I am placing more emphasis on things the groups can do that hydrogen can't rather than the things hydrogen can do that the groups can't

You could say the same about the tetrel group too
 

Hydrogen's valence electron configuration is 1s1, whereas the tetrels have a valence electron configuration of ns2np2.

Hydrogen is monovalent (1 valence electron), whereas the tetrels are tetravalent (4 valence electrons).


Although, this is also a difference due to the first electron shell only holding two electrons, it is an interesting difference to note:

"Various tetrels can come in the form of allotropes (carbon [ex. graphite, diamonds], silicone [amorphous, crystalline]) whereas hydrogen does not."

I wish I knew an adequate definition of the groups, because I would like to say that it should be in all three ... or at least two of the three, except it is possible that part of the intent of the groups is to have only one group per element and not just list out properties.
If that is the case, or if we want the groups to have and not have very specific properties (more specific "definition" ... more exclusionary) ... then I would say that it should be in it's own group.

Personally, I would like to see Helium labeled as a noble gas, but placed about the 2nd column because of its electron (cloud) structure
 

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Discussion Starter #7
I became interested in this because I'm actually in an entry level chemistry class. I thought it was silly when my teacher said it's above the alkali metals due to its electron structure being like that of the alkali metals yet can also be like a halogen at the same time ("come on, which is it?!" I thought). So me being who I am, I decided to do research on this topic on my own (was definitely not satisfied with what my teacher said [figured there must be more to the story!]). It's interesting because as it turns out, where hydrogen should be located is still a debate.

To me, that's actually shocking considering where it's been ever since the creation of the periodic table back in the 1860s. Naturally, my teacher probably wasn't going to discuss this to "keep it simple" and not confuse the other students. That or she just doesn't feel like getting into that topic, which would probably take no more than 10-15 minutes to briefly discuss IMHO.

To make things even more interesting, some have even suggested removing not just hydrogen but also helium from the "periodic law" altogether and having hydrogen AND helium in their own group.

http://books.google.com/books?id=yPtSszJMOO0C&pg=PA281&lpg=PA281&dq=hydrogen+arguments+periodic+table+placement&source=bl&ots=emW0OJEvDT&sig=tPN7zsdv5taG6f1LANkxQJ8-Dlw&hl=en&sa=X&ei=c8yXUOvUOYq09QTruYC4AQ&ved=0CG4Q6AEwCQ#v=onepage&q=hydrogen%20arguments%20periodic%20table%20placement&f=false

Your post is very aesthetically pleasing.

My take on it: hydrogen is part of the hydrogen group.
Oh why thank you! I tried my best to make it look nice. I would've put in more content but I realized it would've been probably way too wordy if I didn't do charts (there's TMI about this to keep this post clean looking lol). There is still a lot of links but I figure that if some people come along researching the same topic they may come across this thread and have a lot of information all in the same place :happy:.
 

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Discussion Starter #8
:laughing:

Hydrogen is neither, Hydrogen is in a class of its own. In fact I believe that Frank Sinatra wrote a song dentitled "My way", that was actually dedicated to Hydrogen. :tongue:

All the chemical properties arise from the quantum mechanics involved, the periodic table is the way in which we try to make sense of these trends. I would say that the properties of Hydrogen is quite unique.

Also, did you know that most elements have been shown to have metallic electronic states at very high pressures, where the energy gap between the valence band and the conduction band closes. Metallic hydrogen is said to exist at the centre of very dense gas planets. Metallic oxygen exists in stars and hence astronomers refer to the presence of oxygen and heavier elements relating to the level of "metallicity" of stars.
That's an interesting fact about the elements actually (thanks for sharing!). I tried looking up information about hydrogen and that song and I didn't find anything :sad:

I'm making a presumption here feel free to correct me, but it's like alkalis because it's only got 1 electron to empty it's shell, it's like halogens because it only needs 1 electron to fill it's shell, and it's like carbon because it's halfway between having either emptied it's outer shell or filled it's outer shell.
That's somewhat the gist of the argument :happy:. Love your signature btw lol :crazy:.

I tried looking up definitions of "alkali metal", "halogen" and "tetrel" - but they were not helpful, they just listed the elements in the group lol

I would not mind Hydrogen being considered part of several groups (I don't see why it can not).

Looking at the different column with alkali metals and with halogens ... its biggest differences seems to be from only having on electron shell (which is a big enough difference, but only helium shares that trait ... a few others do as well after they lose an electron)
 

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)

Halogens can have a large atomic radius, whereas hydrogen has a very small atomic radius.

Halogens have a valence electron configuration of Nsn, whereas hydrogen has an electron configuration of 1s1


Although being able to gain and lose an electron is a significant note, I am placing more emphasis on things the groups can do that hydrogen can't rather than the things hydrogen can do that the groups can't

You could say the same about the tetrel group too
 

Hydrogen's valence electron configuration is 1s1, whereas the tetrels have a valence electron configuration of ns2np2.

Hydrogen is monovalent (1 valence electron), whereas the tetrels are tetravalent (4 valence electrons).


Although, this is also a difference due to the first electron shell only holding two electrons, it is an interesting difference to note:

"Various tetrels can come in the form of allotropes (carbon [ex. graphite, diamonds], silicone [amorphous, crystalline]) whereas hydrogen does not."

I wish I knew an adequate definition of the groups, because I would like to say that it should be in all three ... or at least two of the three, except it is possible that part of the intent of the groups is to have only one group per element and not just list out properties.
If that is the case, or if we want the groups to have and not have very specific properties (more specific "definition" ... more exclusionary) ... then I would say that it should be in it's own group.

Personally, I would like to see Helium labeled as a noble gas, but placed about the 2nd column because of its electron (cloud) structure
You WOULD suggest it being part of multiple groups, @Mr. Meepers! It does kind of suck when they don't give you an actual definition but just what constitutes the group, doesn't it? (probably best to try searching for their common properties). I think it's interesting that even though there aren't too many physical properties hydrogen has with the carbon group directly, there are literally over 15 million hydrogen-carbon and hydrogen-carbon-element X substances in existence (and counting); carbon + element X substances around 47,000; and a little over 48,000 hydrogen + element X substances (found in the article arguing for hydrogen being placed above carbon).

I would do a CAS search as mentioned in that article myself but am gonna have to learn how to use the CAS search engine before coming up with that information myself (since I like to see it all for myself ^_^ ).
 

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Subscribed because there's some good lookin' information in here, but a long read...
Yeah I tried to consolidate everything the best I could, thus the tables I created. Tbh this post took me quite some time (Idk if you wanna know just how long lol) to put together. I was really quite surprised with how much information is out there in regards to where hydrogen should be placed on the periodic table.
 

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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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