The discovery of hafnium, element number 72, provided a controversial episode in chemistry. G. Urbain, a French chemist, claimed in 1911 to have isolated an element number 72 from a sample of rare earth (elements 58–71) compounds. However, Niels Bohr believed that hafnium was more likely to be found along with zirconium than with the rare earths. D. Coster and G. von Hevesy, working in Bohr's laboratory in Copenhagen, showed in 1922 that element 72 was present in a sample of Norwegian zircon, an ore of zirconium. (The name hafnium comes from the Latin name for Copenhagen, Hafnia). (d) Using their electron configurations, account for the fact that Zr and Hf form chlorides MCl₄ and oxides MO₂.

Video transcript

Hello. Everyone in this video, we're saying that both aluminum and gallium form chlorides of M. C. L. Three. So M being the medal And oxides as M. 203 and we're trying to write out the electron configuration or the condensed electron configuration to explain why this is. So first let's take a look at aluminum. So A L. Let's go ahead and write out the condense electron configuration. So a L element is going to be right over here in this black outline. So doing a noble gas configuration, refining noble gas closest to this element, not moving forward but backwards. So going backwards we arrive at neon and neon is going to be the noble gas that we're using, putting this in brackets and that's indicating our new starting point of the electron configuration. So over here they were reading down we get to this let's go ahead and so label the road numbers to make it a little bit easier. Alright, so right here we're going to go over here. So this is our third row. We're going to be in this S block And we're reading one and 2 elements. So that's going to be three for the road number as for which block and two of how many elements we have read. So continuing on two right here now again still were in the third row but now we're in the p block and we're only reading one element so three P. One next we have our gallium. So G. A. That's going to be right over here and again doing the noble gas configuration. We're going backwards to this argon and that's going to be our noble gas. So again in brackets we have our A. R. Then reading continuing to read this right here, fourth row and the S block reading both of these. So That's going to be four S 2. Now this over here, this is our D block. Our D block is a little bit weird in regards to the electron configuration. Unlike writing out just the 4th row Brass Street going to subtract one from the original row number. So 4 -1 is three. We're in the D Block or Reading all the way across. So 10. Right, We have 123456789 and 10. Now we've landed over here in our p block in the 4th row. So that's four P and one. So as you can see from the highest quantum number orbital's, we have three for aluminum and we have four for gallium. So for aluminum we have two plus one, we have three advanced electrons. And this three electrons can bond with each chlorine atom to form that compound. And then as well as the oxygen, same thing making Singapore with each oxygen to have Those three connected to each other. Now for the gallium here, I'll put this in green we have to and one and again two plus one is three. So we have those three bands electrons to make these compounds possible. So because each compound does have a metal ion with a three plus charge, again, we're doing that criss Cross method. So with the three pledges charge and both aluminum and gallium lose three electrons to form ions to have this compound be possible. And that is why we have this behavior for aluminum and gallium. Thank you all so much for watching.