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For context: I got a question asking, "Which of the following alkaline earth metals do not give flame colour?". I quickly marked $\ce{Be}$ and $\ce{Mg}$ and got negative marks.

The following is a quote from my book (emphasis in the original):

The elements of Group 2 include beryllium, magnesium, calcium, strontium, barium and radium. These elements with the exception of beryllium are commonly known as the alkaline earth metals. These are so called because their oxides and hydroxides are alkaline in nature and these metal oxides are found in the earth's crust.

As you can see, it's stated that beryllium is not an alkaline earth metal!

Is beryllium an alkaline earth metal or not?

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    $\begingroup$ Shriver & Atkins 6th ed: "The elements calcium, strontium, barium, and radium are known as the alkaline earth metals, but the term is often applied to the whole of Group 2." (p 336) It actually excludes Mg too. (And I am not saying that it is an authoritative source on chemical nomenclature.) Greenwood & Earnshaw simply refer to the whole of Group 2 as the alkaline earth metals. $\endgroup$ – orthocresol Feb 15 '16 at 17:41
  • $\begingroup$ Are you preparing for JEE ? And by the way , I feel yours answers is correct since Be and Mg do not give flame test. $\endgroup$ – Akshay Pratap Singh Feb 15 '16 at 17:57
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    $\begingroup$ It's not. The picture is from NCERT book @AkshayPratapSingh $\endgroup$ – Aditya Dev Feb 15 '16 at 18:11
  • $\begingroup$ Self-teaching worker has already answer the question. Regarding the negative marks you got Be is exceptionally small. And hence hold its electrons tight enough not to be excited by oxidizing flame. $\endgroup$ – user411518 Mar 10 '17 at 13:56
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There is some disagreement in usage among authors, but IUPAC standard nomenclature approves calling beryllium an alkaline earth metal, as explained on page 51 of IUPAC's last Red Book.

In fact, all the elements belonging to group 2, $\ce{Be,Mg,Ca,Sr,Ba,Ra}$, are called alkaline earth metals with IUPAC's approval.

Other common traditional names approved by IUPAC are alkali metals for the elements of group 1 except hydrogen, i.e. $\ce{Li,Na,K,Rb,Cs,Fr}$; halogens for $\ce{F,Cl,Br,I,At}$ in group 17,whose only member excluded from such a designation is $\ce{Uus}$ (now $\ce{Ts}$), and noble gases for all the elements of group 18 except $\ce{Uuo}$ (now $\ce{Og}$), i.e. $\ce{He,Ne,Ar,Kr,Xe,Rn}$.

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Alkaline metals are called so because of two reasons:

  1. They are obtained from the earth in the form of ores

  2. Their oxides and hydroxides show basic (alkaline) natures.

Beryllium fulfills the first criterion but not the second one, since its oxides and hydroxides show amphoteric behavior, rather than alkaline. So, it is not considered an alkaline earth metal in the true sense, even though it does resemble them in various other properties.

So, if asked which group 2 metal is not considered an alkaline earth metal, then your answer should be beryllium. Otherwise, you should probably consider beryllium as an alkaline earth metal.

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  • $\begingroup$ Praveen, I made some major edits to your answer for readability. If you don't like anything I did, or if I misrepresented what you were trying to say, please feel free to edit it further. Thanks for posting here! $\endgroup$ – hBy2Py Mar 10 '17 at 15:01
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If we're going to be fussy about alkaline earth metals being "alkaline earth" in the proper sense, then there are only two of them: calcium and magnesium. Beryllium oxide fails to be alkaline and the heavier Group 2 oxides (or, the hydroxides formed upon reaction with water) are too readily soluble to really be "earth-s" (hyphen included because my device autocorrects the word without the hyphen).

Compared with the other Group 2 metals, calcium and magnesium are so ubiquitous that they're basically (no pun intended) the namesake for the whole group. Thus as IUPAC asserts the phrase "alkaline earth metals" has spread to all of Group 2.

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I think Be is not an alkaline earth metal as its oxide is not purely basic in nature, it is amphoteric. Also its oxide is not found in Earth crust so it must not be an alkaline Earth metal.

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  • $\begingroup$ Sarang, this answer lacks a bit of supporting material to back up the claims. I'm not sure it adds anything to the already excellent answers. $\endgroup$ – jonsca Sep 3 '17 at 22:09

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