The chalcogen-group of elements (eldfrumefnin)

1) Selenium and tellurium
Non-metals and metals bordering the metalloids are sometimes called near-metalloids:
Nonmetals in this category include carbon, phosphorus, selenium and iodine. They exhibit metallic lustre, semiconducting properties and bonding or valence bands with delocalized character. This applies to their most thermodynamically stable forms under ambient conditions: carbon as graphite; phosphorus as black phosphorus; and selenium as grey selenium. These elements are alternatively described as being 'near metalloidal', showing metalloidal character, or having metalloid-like or some metalloid(al) or metallic properties. http://en.wikipedia.org/wiki/Metalloid

The four málmfrændar (metal cousins) or near-metalloid non-metals

The icelandic terms for "metalloid" mentioned in the Orðaskrá um eðlisfræði og skyldar greinar (Icelandic terminology list of physics and related fields)  are: málmbróðir (lit. "metal-brother"), málmungur (used in the Icelandic wikipedia article) and melmingur. The term hálfmálmur is the translation of "semimetal", which is used to denote physical, not chemical properties like "electrical conductivity".  Many of the elements that are semimetallic are metalloid in their chemistry but the two terms should not to be regarded as being synonymous.
The Icelandic term I create for "non-metallic near-metalloids" (carbon (C), phosphorus (P), selenium (Se) and iodine (I) is an extrapolation of "málmbróðir" (metal-brother): málmfrændi (metal-nephew).  The name for the "more metallic metalloids" (Aluminium (Al), tin (Sn) and bismuth (Bi) could be "nærmálmur".
If you look at the initial image of the periodic table on the English wikipedia site on metalloids you see that selenium is the only one that is marked pink, which refers to its being uncommonly included in the list of metalloids, unlike carbon, phosphorus and iodine (marked in yellow), whch are rarely included. Polonium is a "nærmálmur" and astatine is so radioactive that its is very difficult to establish its place on the chemical spectrum between metallic and non-metallic. This means that selenium is actually the "prototype of a "non-metallic near-metalloid". It is the only element that has left chemists in doubt about its addition to or exclusion from the list of metalloids, it is a málmfrændi (metal-cousin). This means that the term málmfrændi on its own could already do well as a name for selenium. But there's a way we can terminologically isolate the element more thoroughly and in the proces create a name for its chemical brother telerium in a way that we end up with the same terminological harmony that is found in the existing names: tellurium (named after the Roman earth-godess Tellus) and selenium (named after the moon-godess Selene).

The elements marked in red are metalloids (málmbræður), those in orange are the non-metallic near-metalloids (málmfrændar), those in yellow the non-metals (málmleysingjar) and the halogens (söltungar) in pale-yellow. Those marked in lilac are the nærmálmar, the "more metallic near-metalloids". Outlined in green are the elements that are named after female entities: Vanadium after Freyja (Vanadís), Niobium after King Tantalos' daughter Niobe, Palladium is called after the asteroid Pallas, which in its turn was derived from the nick-name of the Greek godess Athene, Iridium after Iris, the godess of the rainbow.  Note that these four are all metals. Apart from metallic elements, there are only two elements named after female entities: selenium and tellurium, respectively named after the Roman moon- and the earth-godess. This means that we can perfectly isolate selenium and tellurium by making reference to these female entities. We can do this by femininizing the kinship term "frændi" to "frænka" for selenium: málmfrænka and "bróðir" to "systir" for tellurium (málmsystir).

Some say that both elements were named just after the moon an earth and not the godesses.  But that's not important.  Both names are feminine in their languages of origin.  In her book "Discovery of the elements", Mary elvira Weeks writes: "Since Klaproth had named tellurium for the earth, Berzelius thought it appropriate to call the SISTER-element for the earth's satellite."  If you google "selenium" along with "sister-element" you get a lot of results, while googling it along with "brother-element" yields none.  This gives me confidence that the use of the female equivalents of "málmfrændi" and "málmbróðir" for selenium and tellurium respectively is fully appropriate.

The good thing about these terms is that they reflect the terminological harmony found in the international names of the two element.  When we include these terms in the list of names of the oxygen group of elements, the slight increase in metallic properties from oxygen to polonium is nicely reflected:  ildi and brennisteinn (judging from the names, these are no metals), málmfrænka (slightly more metallic that sulphur, but not yet a true "málmbróðir"), málmsystir (the metallod named after a female entity) and maríublý (polonium, a near-metalloid metal named after Marie curie. The element is situated two places to the right of lead, which is the reason I took "blý" (lead) as the second element. "Blý" also emphasizes the more metallic character of polonium.

2) List of oxygen-group elements:

1) Oxygen: ildi (súrefni, OR fúrefni, fjörloft, ozone: bláildi (blue oxygen), þrildi (three-oxygen, contraction of þrí-ildi)
2) Sulphur: brennisteinn (OR hveragula, múspellsmold, ildisbróðir, surtshallur, surtssand. Existing synonyms could be the danicism svola, from svolustaukur (eldspýtnabaukur, from Danish svovlstik), fiði, a neuter form of fiða (Íslensk Orðsifjabók) or fiðusteinn ( http://lexis.hi.is/cgi-bin/ritmal/leitord.cgi?adg=daemi&n=108646&s=128870&l=fi%F0usteinn )
3) Selenium:
1) málmfrænka (The near-metalloid non-metal (málmfrændi) named after a female entity) the moon godess Selene.
The only other possibility is melmingur, the third and least used of the three terms for metalloid mentioned in the Orðaskrá um eðlisfræði og skyldar greinar (the other ones are málmungur and málmbróðir).  Because the i-shift in melmingur makes it sound less like málmur than málmungur, it could be interpreted as "less metallic in its chemical properties".  In this respect it could serve as a name for the near-metalloid non-metals carbon, phosphorus, selenium and iodine.
2) kísmelmingur: Selenium, due to its being a homologue of sulphur it is always found associated with the latter in nature, like in the iron-sulphide mineral brennisteinskís or simply kís (pyrite) as iron selenide (FeSe). A term that emphasizes this property is kísmelmingur (the non-metallic near-metalloid in pyrite)
3) nýbrennisteinn.  The prefix neo- (used in "neon", because it was the new, second noble gas to be discovered after argon, the rare-earth element neodymium because it was the new element isoleted from dydymia. Selenium was discovered after tellurium, but this element doesn't compare in its similarity to selenium.  I abandoned the idea of creating a compound with "brennisteinn" for selenium (like "brennisteinsbróðir", because of the resulting word-lenght, but the prefix ný- is extremely short.  nýbrennisteinn (neosulphur, neothium, neo- + thio- + -ium) isn't exaggeratedly long.


4) Tellurium:
1) málmsystir (The female metalloid (málmbróðir), the metalloid named after a female entity, which can only refer to tellurium, no other metalloid is named after a woman or godess or alludes to something feminine whatsoever.
2) drottningarmálmungur, drottningartin, kóngamálmungur, kóngatin, hirðmálmungur: Tellurium is the predominant element in nature that can form chemical compounds with "gold", the classical "king of metals", like calaverite AuTe₂ and sylvanite AgAuTe₄.  Gold itself is usually found uncombined, but when found naturally as a chemical compound, it is most often combined with tellurium. A few rare non-telluride gold compounds such as the antimonide aurostibite, AuSb₂, and bismuthide maldonite, Au₂Bi, are also known, but they hardly compromise the validity of the term " royal metalloid" as a designation of tellurium. Aqua Regia (Kóngavatn) was so-named because it dissolved gold and in the same way we can call the metalloid that predominantly binds to gold the "royal metalloid", "royal tin" or "queen tin", which emphasizes the fact that it was named after a female deity, the Roman equivalent of the Greek Gaia, Tellus.  Klaproth isolated tellurium from the mineral Calaverite (AuTe2), and he could have named the substance after this unique property, but, instead, he named it, in his words, "von der alten Mutter Erde entlehnte" Tellus.
3) Sjöborgartin: (Transylvanian tin): The type-locality of elemental tellurium is Facebaj, Transylvania and many gold-telluride minerals are found there.  http://webmineral.com/data/Tellurium.shtml It was also in Facebaj that the metalloid was discovered in 1782 by Franz-Joseph Müller von Reichenstein in a mineral containing tellurium and gold.  It is funny that tellurium, the element with its type-locality in Transylvania, the so-called 'land of vampires' produces a "garlic breath" on overexposure.
4) múspellstin, surtstin, brennitin: An good alternative name for the collective term chalcogens (meaning the "ore-formers", since 65% of the earths crust is made up by sulphur and oxygen compounds), as the oxygen-group of elements are sometimes called would be "the elements of fire" (eldfrumefnin, shorter than the troublesome málmgrýtamyndarar), because the first two elements, oxygen and sulphur, have been linked up with "flammability" throughout the history of chemistry : ildi (oxygen, derived from eldur (fire) and brennisteinn, brimstone, sulphur, the substance that was regarded, because of its properties as being the intermediate between the classical elements "earth" and "fire" in antiquity). From the viewpoint of Nordic mythology, the logical fuel of the fiery world of Múspellsheimr would be "brimstone", which is comparable to the christian idea of hell as a place smelling of burning sulphur. This means that the genitive of names like Múspells-,  Surtr (Surts-) or brenni- (in brennisteinn) could be useful to accurately position the "postsulphuric chalcogens" Se, Te and Po.
Brennitin would be the equivalent of Brimtin in English. The prefix brim-in brimstone is actually a corruption of the Old English word for "burning" and is unique to this compound, unlike the uncorrupted brenni- in the Icelandic equivalent brennisteinn. So it is easy to coin pure English names for tellurium (brimtin) and polonium (brimlead). But even in Icelandic, if you would ask an Icelandic chemistry professor what element could alternatively be refered to as brennitin (yes, tellurium burns, not as intensely as sulphur, but still, and also the appearance of the element is refered to as "tin-like"), he would horizontally search the latter part of the 5th period, where tin is situated, while running down the list of postsulphuric chalcogens (Se, Te and Po) and easily end up at the place where tellurium is situated.
"Kístin "(pyrite-tin) is an erroneous term!
In contrast to selenium, tellurium is not in general able to replace sulfur in its minerals, due to the large difference in ion radius of sulfur and tellurium. In consequence, many common sulfide minerals contain considerable amounts of selenium, but only traces of tellurium.  So, watch out, I made the mistake, don't call tellurium "the tin in pyrite!". See http://en.wikipedia.org/wiki/Tellurium

5) Polonium
1) maríublý: Polonium is situated just two places to the right of lead (blý) and most of its exceedingly radioactive isotopes represent one of the last stages in the three major decay-chains that end up with lead-isotopes. This makes blý an appropriate choice for a second element in a compound. As for the first part: because the element was discovered by Marie Curie, who named it after her country Poland, it would be appropriate to name it after her.
2) Læsamálmur, Læsaefni, Læsablý: The first part of this compound is an Old Icelandic name for the Polish people: Læsir (masculin plural of Læsur). The Íslensk orðsifjabók mentions:
Læsir, †Lḝsir, Lesir k.ft. † pólskur þjóðflokkur við Vislu, Ljachar, sbr. frúss ljachy 'Pólverjar', lith. lénkas og fpól. lęchь (s.m.) sem er samdráttarmynd (með smækkunarviðsk. -ch) < lędĕninь af lędo 'nýtt land, óbrotið land', eiginl. 'nýlendingar'. Sk. land
Marie Curie was born in Warsaw, which is situated at the Vistula River, so Læsur applies to her, Læsynja, the feminine form of Læsur is even more specific: Læsynjumálmur, Læsynjublý (metal, lead of the Polish woman)
In the early 11th century, Scandinavians referred to the Polish tribe of Polans in the region of Gniezno as Laesar. (see http://en.wikipedia.org/wiki/Lendians and http://en.wikipedia.org/wiki/Polans_(western)
Note that the typically Polish name Lech, which is the first name of the former Polish president Lech Walęnsa, happens to have an Icelandic variant!
The term Lechitic is related to the name of the legendary Polish forefather Lech and the name Lechia by which Poland was formerly sometimes known. http://en.wikipedia.org/wiki/Lechitic_languages
The orðsifjabók also mentions Læsir as a masculine personal name, which is identical to Lech, so Icelandic actually has a form of its own for this typically Polish name: Læsir Valensa (Lech Walęsa, in which the normally nasal sound ę is colloquially pronounced as 'en', so I adapted it to Icelandic as 'en'.
1) Læsir, †Lęsir k. † karlmannsnafn (í fornaldars.) Vísast tengt þjóðflokksheitinu Læsir (3) Íslensk orðsifjabók (see above)
3) púlín, púlínablý, púlínamálmur
If the word has to be constructed in the same style as most other names, where the ending -ium is replaced by -ín (natrín, kalín, kalsín, why not calling polonium PÚLÍN, instead of 'pólon', after the oldest Icelandic form Púlínaland, mentioned in the Þiðreks saga af Bern: En er Vilkinus konungr hefir stýrt þessu ríki um stund, þá býr hann her sinn ok ríðr með ótal riddara ok annarra hermanna út í Púlínaland ok á þar margar orrostur ok stórar bæði.
is a nærmálmur (more metallic near-metalloid). I named it after Marie Curie and the fact that it is situated two places from lead and because almost all of its isotopes ultimately desintegrate into lead isotopes.