Talk:Halogen

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Halogens[edit]

just to note that the halogens are not group 17 but in fact group 7 elements. the transition metals in the periodic table are not given group names but are just a block of elements

IUPAC group numbers are used. Femto 18:52, 25 May 2006 (UTC)
The preceeding statement is incorrect; the former convention was that the s and p-block elements were groups I-VIIIA while the transition metals were given values of I-XB. The current IUPAC convention however is that the s, p, and d-block elements are labelled groups 1-18, which lands the halogens at group 17 (former VII or VII A). This leaves the f-block skipped but that's a whole other can of worms... dhall27 18:46, 06 Oct 2008 (UTC)
I disagree with your statement that the preceeding statement is incorrect, as I have 2 books on me now (Heinemann OCR AS Chemistry by Dave Gent and Rob Richie, and CGP AS-Level Chemistry OCR-A by Mary Faulkner, Sarah Hilton, Paul Jordin, Sharon Keeley, Simon Little, Andy Park, Antonio Angelosanto, Vikki Cunningham, Ian H. Davis, John Duffy, Max Fishel, Emma Grimwood, Richard Harwood, Lucy Muncaster, Glenn Rogers, Derek Swain, Paul Warren and Chris Workman) for my AS chemistry course, which both say that the halogens are in grouip 7, as 'user:Femto' said, and not in Group 17. — Preceding unsigned comment added by Ohdear15 (talkcontribs) 10:24, 5 December 2011 (UTC)
I am well aware that syllabi up to the high-school level often refuse to use the IUPAC group numbering. This makes sense at that level where the d-block groups are not important and there is a desire to correlate the group number with the number of valence electrons: indeed, apart from the first row (scandium to zinc), very few d-block elements get mentioned (definitely silver, and perhaps palladium and platinum for hydrogenation of alkenes and alkynes; I suppose tungsten, gold, and mercury might vaguely count as household names). However, we do not stop at that level on WP, and we can very easily get into contexts where the d-block groups are important. The historical way to deal with this was to append "A" to the group numbers on the left side of the table and "B" to those on the right side, but it gets really confusing (especially as the USA and Europe followed opposite conventions for this), so IUPAC sorted it out with the 1–18 numbering. And that is what we should use, and thankfully do use, here, as does every inorganic chemistry textbook the moment you step into university. Double sharp (talk) 14:03, 3 November 2016 (UTC)

Ugly[edit]

Could this page get any uglier? A figure to the left, a table to the right, another two to the bottom. All squashing the main text into a strange, central region. It's horrible. Suggestions? --Plumbago 15:54, 24 October 2006 (UTC)

I agree, it's ugly. I moved things around and added section breaks. I think it looks better, but it could still use some work. I don't know what to do with the "Explanation of above periodic table slice:" thingy. --Ed (Edgar181) 16:25, 24 October 2006 (UTC)
Nice work. It's much better. I agree about the "explanation" table. It's much bigger than the table it describes. Perhaps the periodic table slices need an "explanation" tab at the base which links to a seperate page? That's not ideal either, but might make more sense. Regarding said "explanation" table - it appears to contain an error. Elements are described being as either "naturally radioactive" or "radioactive, synthetic" elements. The former should really be "radioactive, natural" n'es pas? Cheers, --Plumbago 16:47, 24 October 2006 (UTC)

Interhalogens section is unsound and needs cleaning up[edit]

Why would AtBr and AtI be the commonest interhalogen compounds, given the extreme rarity of astatine? The compounds are not particularly like the halogens either: ICl is not soluble in carbon tetrachloride whereas the halogens are (incipient metallic properties of heavier halogens begin to show through). Dajwilkinson 02:43, 12 May 2007 (UTC)

In existence?[edit]

Why is Fluorine said to be the most reactive element in existence? Can we really be certain there isn't another element yet to be discovered that is more reactive than fluorine? 82.18.181.78 22:34, 10 February 2007 (UTC)

We should change it to "Flourine is the most reactive chemical in existence known to man" Chuck61007 22:36, 27 March 2007 (UTC)

"Flourine is the most reactive chemical in existence known to woman" 88.88.102.73 (talk) 18:54, 15 October 2011 (UTC)

Why do we need "in existence"? Could the author perhaps provide references to more reactive elements which are not in existence. — Preceding unsigned comment added by Chrisbaarry (talkcontribs) 13:55, 8 November 2014 (UTC)

Major reversion[edit]

I reverted the article to the last version by 8thstar [1]. This was because that's the most recent version that is more or less factually accurate. Some of the recent changes were blatantly inaccurate, to put it mildly. First, halogens are not "radioactive in their natural states as diatomic molecules", with the exception of astatine. The book that was used to justify that point certainly does not say that. Second, the contribution of d-orbitals to bonding in hypervalent compounds is at the very least disputed, if not widely discredited. A textbook from 1975 is not a good reference to back this statement. See the references in the article about hypervalency; one author talks of "the nearly unanimous conclusions of theoretical studies that the octet rule is a valid first approximation for the entire main block and that it is the traditional Lewis 2c-2e model of covalent bonding that requires modification" (Jensen, 2006). --Itub 12:29, 15 March 2007 (UTC)

Also, i removed the "When under standard conditions" barf; that suggests that when they are *not* under standard conditions, they are as halides. Pressure, etc have nothing to do with their existance as diatomic molecules because they're so reactive that even under them, they'd just not really be found. SConfident.gif J O R D A N [talk ] 18:05, 15 March 2007 (UTC)

I wrote under standard conditions (what does barf mean?) to replace the phrase in their natural form which is ambiguous. Yes, halogens are not found in their elemental (diatomic) form in the environment. But they are not always found as halide ions - iodine, for instance, commonly exists in nature as iodate, IO3. I feel the introduction to this article should be tightened. There is quite a lot of rambling - it should be more consise.
Ben 20:10, 15 March 2007 (UTC)
Firstly, i apologise for the use of "barf", it was supposed to be b0rf as a friendly gesture.
What i meant by it was that even though you're right, it made it sound that if halides were placed under standard conditions, there would be a yield of halogens; reactions occuring under standard condtions are, from my experience with their use, a "buffer" in that they allow comparable data sets where similar reactions are semi-ensured, and to use the context of standard conditions makes it sound that they only occur under standard conditions and despite being correct to some extent, makes it sound more ambiguous than needed.
I think the introduction as it is (current revision) is horrendous, and i'd prefer a more concise introduction. If we could come to a compromise, i'd be happy. SConfident.gif J O R D A N [talk ] 09:43, 19 March 2007 (UTC)

I think you are right. it sucks. —Preceding unsigned comment added by 72.15.87.185 (talk) 20:47, 8 September 2008 (UTC)

Uses[edit]

A section describing uses might be helpful, e.g., halogen headlights for automobiles. Virgil H. Soule (talk) 16:30, 27 December 2008 (UTC)

What does this even mean?[edit]

Chlorine has minimal solubility in water, with maximum solubility at 49.3°F (9.6°C) when approximately 1% is dissolved.[3]

The reference listed doesn't even hint at this figure. This is a maximum in that experimental curve where the lowest temperature is 278K. Not really rigourous scientific study and certainly not a "maximum". More likley the maximum would be at the temperature as close to 0K as we can get.

Also, is this 1% by mass? 1% of the chlorine bubbled through the water? I have changed this to a more sensible figure, 0.7g Cl2 per kg of water at ambient temperature (21oC). If this is a problem please change back. —Preceding unsigned comment added by 80.225.11.94 (talk) 06:00, 8 April 2009 (UTC)

Halogens: three phases[edit]

Okay, I know Halogens exist in three phases at room temperature -> fluorine and chlorine are gases, bromine is a liquid and iodine is a solid at ROOM temperature. I'm not sure what the deal with standard temperature is though. Maybe someone can clear this up or fix the mistake? Winderful1 (talk) 23:01, 16 November 2009 (UTC)

See standard temperature and pressure. Double sharp (talk) 09:05, 7 October 2012 (UTC)
With the decent possibility of Copernicium being gaseous at standard temperature and pressure, perhaps the sentence in the article should be revised, because if it is, group 12 elements will have one of each of the 3 states. I don't know enough about it, though... --Smauler (talk) 02:40, 11 August 2013 (UTC)
I'm not inclined to do that until we have solid experimental proof of the state, though...we should perhaps look into Fm–Lr (the melting points are just predictions). Double sharp (talk) 03:22, 11 August 2013 (UTC)
Yup, Cn is almost certainly a gas based on current data. It should be noted that we do not have direct experimental proof of this, though, but merely inferred it from properties we can measure. (After all, it does not make much sense to assign a phase to 3 atoms.) Double sharp (talk) 13:58, 3 November 2016 (UTC)

Hydrogen Halides[edit]

This section describes the hydrogen halides as a "series of particularly strong acids." While they are all highly reactive, hydrofluoric acid is defined as a weak acid (it does not completely ionize in an aqueous solution). Change this maybe? strong ==> reactive would remove the inaccuracy, but it might not be the best wording. —Preceding unsigned comment added by 199.99.251.85 (talk) 17:06, 25 November 2009 (UTC)

This whole section seems repetitive and unclear. The first paragraph seems to contradict itself - if the stated reaction applies to "all of the halogens", would it not apply to hydrogen iodide and hydrogen astatide, even though they may subsequently break up? The third paragraph ("All halogens form binary compounds ...") seems to be written as an introduction, and duplicates much of the first. And as a non-chemist I must agree that it is confusing to describe hydrofluoric acid as a "weak acid", and then describe hydrogen fluoride as "highly acidic" in the next sentence (so highly acidic that it can react with glass - previous section on Characteristics - Chemical).Doc.Ian (talk) 16:02, 3 April 2016 (UTC)

Incandescent lightbulbs[edit]

The sentence: "This enables the production of lamps that are much smaller than incandescent lightbulbs at the same wattage." implies, incorrectly, that halogen light bulbs are not a type of incandescent filament bulb. Would it not be better to replace the term "incandescent lightbulbs" with "conventional incandescent lightbulbs" or "inert gas filled incandescent lightbulbs"?

Chrisbaarry (talk) 13:26, 8 November 2014 (UTC)

Fixed. SBHarris 19:36, 8 November 2014 (UTC)

Relative abundance[edit]

"Chlorine is by far the most abundant of the halogens,"

Should this be qualified somehow? Particularly since the chlorine article says (of chlorine): "It is the second most abundant halogen and 21st most abundant chemical element in Earth's crust."

In what context is chlorine the most abundant halogen?

Chrisbaarry (talk) 14:19, 8 November 2014 (UTC)

In seawater. I've fixed that by insertion of the word.
In so far as elsewhere it will take a paragraph to sort. In the universe the abundances of F and Cl are flipped due to the way they are made in stars. On Earth the halogens decrease in abundance with atomic number Z, though F and Cl are closer than you'd guess from just Z. In seawater the higher solubility of Cl against Ca puts it far ahead of F. Which is why your veins aren't full of fluoride.SBHarris 19:45, 8 November 2014 (UTC)

External links modified[edit]

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X[edit]

What kind of a halogen is X? 108.66.234.9 (talk) 13:48, 3 November 2016 (UTC)

X is a generic symbol for any halogen when it does not matter which one is being used. (I'll humour you because others might have the same question.) It is just like "M" for metals, "Ln" for lanthanides, or "An" for actinides. Of course, I know you already know that, because you first posted it on Talk:Extended periodic table where it was clearly defined on the article as "X = a halogen", so you are clearly just wasting my time as you did with your unreliable sources back there. Double sharp (talk) 13:55, 3 November 2016 (UTC)

Biological role of fluorine[edit]

The section on biological role of halogens says that "Fluoride anions in very small amounts are essential for humans." however, the source given for that information (http://www.who.int/water_sanitation_health/dwq/chemicals/fluoride.pdf) says nothing of the sort, in fact it says "Fluoride may be an essential element for animals and humans. For humans, however, the essentiality has not been demonstrated unequivocally, and no data indicating the minimum nutritional requirement are available." (emphasis mine.) i propose that this sentence indicating fluorine is an essential nutrient for humans be taken out as i cannot find confirmation of this. morsontologica (talk) 20:01, 6 December 2016 (UTC)

Considering the above i have decided to edit the sentence to better reflect its source material. Input is welcome morsontologica (talk) 20:02, 6 December 2016 (UTC)