We aren't going to worry about why different electronic transitions occur with greater or lesser efficiency that has to do with symmetry and group theory, and some mathematics that we aren't equipped to handle right now. MLCT transitions require much more energy but they happen frequently, leading to stronger absorbances in the spectrum. These electronic transitions interact with photons very efficiently.Īs a result, there is a kind of counterintuitive relationship in the UV-visible spectra of transition metal complexes: d-d transitions require very little energy but occur relatively infrequently, meaning they give very weak absorbances in the spectrum. The electronic transitions involved just are not very good at capturing photons.īy comparison, it might sound like it would be difficult to move an electron from the metal all the way to the ligand, but it's actually pretty easy. That sounds like it might be pretty easy - the electron isn't going very far, after all - but d-d transitions are actually quite inefficient. For transition metals, the valence electrons are in the d sub-shell, and in a d-d transition, the electron is excited from one d level to another. For transition metals, these electronic excitations are called d-d transitions. In addition, sometimes electrons can be excited from one level to another, just on the metal ion. However, these two acronyms are sometimes used interchageably to suggest some sort of transition that involves both the ligand and the metal, without worrying too much about the direction. Sometimes the former case is referred to as a ligand-to-metal charge transfer, or LMCT the latter case would be a metal-to-ligand charge transfer, or MLCT. It involves the excitation of an electron from the ligand to the metal, or vice versa. One very common transition is called a charge transfer transition. These transitions might involve the metal ion itself, or the ligands - those molecules or ions that bind to the metal ion. When they do, there are a number of possible electronic transitions that can result. These transition metal complexes or coordination complexes have lots of electrons, and they can often interact with lots of different photons. These molecules bind to the metal ions, forming coordination complexes. In solution, metal ions would not swim around by themselves, but would attract other molecules to them. Because of their relatively low electronegativity, transition metals are frequently found as positively-charged ions, or cations. Transition metals are often associated with brightly-colored compounds. So I would write the concentration is approximately 0.0969 Molar.\) All right, 0.539 plusĠ.0086 is equal to that, divided by 5.65333 is equal to this, so if we go three significant figures this is going to be 0.0969. So you get 0.539 plusĠ.0086 is equal to 5.65333C, and then divide both sides by this, and you would get C is equal to, is going to be approximatelyĮqual to, be a little careful all of these would really be approximate. And then if you wanna solve for C, let's see, we could add They told us that our absorbance is 0.539, so we know that 0.539 is equal Let me get rid of all of this stuff here. So what this tells us, is that absorbance is going to be 5.65333 times our concentration minus 0.0086. I'm gonna use m and b, and then my final I'll answer I'm going to round to Significant figures here we have have our three, but we could just view the m and the b as intermediate numbers Now we could say significant figures it seems like the small M is equal to this and b is equal to this. Regression line to it and it got these parameters, And this is what I got, so I just typed in these numbers and then it fit a linear And I did that, I went to Desmos and I typed in the numbers that they gave. You could also do that by hand but that's a little bit out These points into a computer and then a computer doĪ linear aggression. Would typically do it, is that they would put And you could say sum y-intercept, if we're a purist about it, then the y intercept should be zero because at a zero concentration, you should have a zero absorbance. We could describe it something like this, that absorbance is going to be equal to sum slope times are concentration. Is a linear relationship between absorbance and concentration. So the way that we would tackle this is we know that there The potassium permanganate? Prior to determining theĪbsorbance for the unknown solution the following calibrationĭata were collected for the spectrophotometer. Of potassium permanganate has an absorbance of 0.539 when measured at 540 nanometers in a one centimeter cell. So I have a question here from the Kotz, Treichel,Īnd Townsend Chemistry and Chemical Reactivity book, and I got their permission to do this.
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