Platinum and the platinum metals

"Hvítagull" for "platinum" is clumsy. In order to make names for the other platinum metals we need a shorter name.  Platína literally means "little silver" in Spanish.  The only word that can reflect the originally spanish etymology and the position of the element on the periodic system next to gold (expressed in hvítagull) is a fusion of the i-shifted forms of "gull" (gylli) and silfur (silfri): GYLFRI

Palladium was almost impossible to translate. meystirnisglit (the metallic lustre named after the asteroid that was in its turn named after the godess Pallas (meaning "virgin" (mey))
With "gylfri" as a flexible name for "platinum" we can easily form a name for platinum's little sister: GYLFRISSYSTIR, RÓFGYLFRI (róf- spectral, but can also refer to the many colours of its salts, for which the element was called after a rainbow (iris)), ÞEFGYLFRI (blágull, osmium),
Rhodium (brynsilfur or brynsilfri, ástblómsilfur),

Eyjasundefni (protactinium)

Protactinium has an unique position on the periodic system of respresenting a strait in the, in nuclear physics called "sea of instability" between two elements that have much more stable isotopes, the so-called primordial nuclides: Th-232 and U-235 and U-238.  The compound "eyjasund" (straight between two islands: ey (island, genitive plural eyja- (islands-) + sund occurs in the old icleandic liteature, nl, the Egilssaga and the Formannsögur. I first thought of the compound "eyjasundbly" (I'm using a stem-compound between "eyjasund" and "efni" instead of a "genitive compound" (eyjasundSblý), because "eyjasund" designates an inherent property of the element, instead of  a geographical location or a type-locality, like in mineralogy.
So the names for protactinium could be: Lísublý (Lizlead (named after Lise Meitner, who discovered the element) or "Eyjasundefni" (isle-strait-element) or "Eyjasundblý" (isle-strait lead)

Hydroxide

Two possible constructions for this term: Hældi or vetnildi

1) Hældi (Há (neuter noun, the name of the letter H, which is the symbol of Hydrogen + "ildi" (oxygen): Há + ildi = háildi or Hældi, as in the Old Norse toponym "Hæmur" (contraction of Há-heimur, in which the "á" was i-shifted, see Orðsifjabók)
2) Vetnildi (vetni + ildi)

Beryllium ragðamálmur

Instead of i-shifting the latter part of "smaragður" (-ragður, "regði"), a genitive plural compound with the latter part of the word is also a possibility: "ragðamálmur".

Lithium: lyndismálmur (mood-metal)

The best name for lithium is, in my opinion "laufsteinsmálmur", the "metal in a leafy stone", so-named because of the leafy flakes in the mineral in which it was originally found, nl. petallite (laufsteinn, laufspat). The metal was named after its MINERAL origin, because the only known alkali-metals known at the time of the discovery, were obtained from PLANT sources. The construction "Laufsteinsmálmur (leaf-stone-metal) is found upon the same idea as what the international name was found upon, its mineral, stony (Greek "lithos", stone), with this difference that the "leafy" nature of the stone must be specified, because "steinsmálmur" (metal form a stone), would make no sense.

Yet, there's another one, this time based on a unique property of the element: "lyndismálmur" ("lyndi" means "mental condition" and refers to lithium use, in the form of compounds, like lithium carbonate (kolsúr lyndismálmur, "carbacidic mood-metal" , for psychiatric conditions like bipolar disorder and schizophrenia.)

Plutonium and Nobelium

Plutonium is the homologue of Samarium in the lanthanide series, which was translated "samreskjumálmur" (samreskja is the Icelandic adaptation of Russian name "samarski", after other Old Icelandic adaptations of Russian toponyms: polotsk (Pallteskja) and Smolensk (Smáleskja).  The construction for plutonium becomes: samreskjublý (samarish lead).

Tungsten:
Another one for tungsten. The international name is "wolfram", named after the nickname  of the mineral scheelite "lupi spuma" (froth of the wolf), because it devoured tin in the smelter. It is, however not necessary make reference to a wolf: átfrauðmálmur (át- (eating away, corroding) + frauð (foam) + málmur (metal), or átfrauðglit, a construction in which "glit" stands for "metallic lustre".

Tungsten (Wolfram)

A new possibility is "Fenrisglit" (Fenrir (wolf in Old Norse Mythology) + glit (metallic lustre)
The other ones are "þungsteinn", "vargfróðumálmur", ylfi (i-shift of "úlfur") and baskamálmur, because it was discovered by two brothers of the Basque Royal Society.