In 1803AD, Osmium was discovered by Smithson Tennant when dissolving an impure sample of platinum in aqua regia, a mixture of hydrochloric and nitric acids. He was able to determine that the black powder left behind after dissolving the platinum was actually a mixture of two new elements, indium and osmium.
•Osmium is a bluish-white and shiny metal.
•Osmium is very hard and is brittle even at very high temperatures.
•Osmium has the lowast vapor pressure and the highest melting point among the platinum group of metals.
•Osmium's density is slightly more than iridium hence is credited as the heaviest element.
Hey there!
Chemical changes are changes in object's chemical compounds and chemical compositions, and often can't be reversed.
Here's an example:
If you have a piece of paper and you happen to burn it, that can't be reversed.
In other words, it can't be "un-burned". Nothing can restore it to its previous state.
Hopefully this helped!
<span>1) The electron configuration of Re is [Xe] 4f14 5d5 6s2
</span>
<span>The ion Re (3+) has lost 3 electrons, so its configuration is </span><span>[Xe] 4f14 5d4
</span>
Then, the number outer-shell d electrons is 4.
<span>2) Sc: [Ar] 3d1 4s2
</span>
Sc (3+) has lost 3 electrons -> <span>[Ar] which has not d electrons.
</span>
<span>Then, the number of d electrons is 0</span>
<span>3) Ru: [Kr] 4d7 5s1
</span>
Ru (4+) has lost 4 electrons -> <span>[Kr] 4d4
</span>
Then, the number of outer-shell d electrons is 4
<span>4) Hg: [Xe] 4f14 5d10 6s2
</span>
Hg (2+) has lost 2 electrons -> <span>[Xe] 4f14 5d10
</span>
<span>Then, the number of outer-shell d electrons is 10</span>