Chemistry question

Question

The transition metal with the lowest melting point.

W

Os

Pt

Ag

could you explain briefly which option you chose

Answer 1

Among the transition metals listed, the one with the lowest melting point is silver (Ag).

Silver has a relatively low melting point compared to the other transition metals mentioned. Its melting point is approximately 961.8 degrees Celsius (1,763.2 degrees Fahrenheit). This is lower than the melting points of tungsten (W), osmium (Os), and platinum (Pt), which have significantly higher melting points. Information on melting points can be found online.

Answer 2

To figure out this question we need to think about a few properties of the atoms. Once we can understand what's going on, the answer will be clear to us.

Melting point is just the temperature that an element will melt at. So if an element has stronger bonds between itself, then the melting point will be lower. Think of two different friendships. In one, the two friends have known each other for many years, and they've got a really strong bond. The 2nd friendship has been only for a few days, and they have a weaker bond. An argument is way more likely to break up the 2nd friendship than the first. Same concept here, if you heat up two different elements, one with strong bonds between itself, and the 2nd with weak bonds, the 2nd will have a lower melting point.

Now how does a transition metal have strong bonds between itself? We have to look at the orbitals. For help on orbitals, shells and subshells, check out the diagram at this link: https://www.quora.com/Can-the-terms-subshell-and-orbital-be-used-interchangeably-If-so-why

Every time the atomic number increases, an electron is added. That electron goes into the electron shell (or orbital). In the d subshells (the ones we worry about when it comes to transition metals), there are 5 different slots. Each slot fits 2 electrons. When we increase the atomic number, for example from Ca to Sc, we will get one electron added to the first shell. If we increase it one more time, from Sc to Ti, the next electron will not go into the same shell, instead it will go to the 2nd shell. We follow up until all 5 shells have an electron, and from then on we add the second electron into each shell. That's why the periodic table has 10 transition elements in periods 4 and 5, because after those 10 electrons fill the 3d subshell, we move onto 4d.

The bottom line is if we add an electron into a shell, we will have more opportunity for that electron to bond to another, leading to a higher melting point. This is the general trend, with an exception when we have 1 electron in all 5 shells, like at Mn, Tc, and Re. At these points, the bonds become weaker, so the melting point drops. Once you go past these elements, the melting point will drop because each time we add an electron, we will lose a lone electron in the orbital, leading to less bonding.

Now let's compare our elements: W, Os, Pt, and Ag. W has the most unpaired electrons at 4, so it will have the highest melting point. Os has all 5 orbitals filled which already lowers the melting point, but then it pairs one of them, making it even lower. Pt pairs an additional two compared to Os, making it even lower than Os. Finally, we can look at Ag, which has the an extra paired electron compared to Pt, leading to it being the lowest melting point.

The transition metal with the lowest melting point here would be Ag.