periodic trends - Ionization energy and Electron Affnity - Chemistry Stack Exchange
Fluorine also has a relatively small atomic radius. . Since the atomic size increases down the group, electron affinity generally . Medicinal products containing chlorine are used to treat infections, allergies, and diabetes. Meek, Terry L. "Acidities of oxoacids: Correlation with charge distribution."J. Chem. Ionization energy (the amount of energy required to remove an Electron affinity (the ability of the atom to accept an electron) decreases down the group. Nitrogen gas is used as a refrigerant, metal treatment, and pressurized gas for oil recovery. The chemical formula for this process is given below. This change in energy is what we call the electron affinity. Ionization Energy: Trends Among Groups and Periods of the Periodic Table.
Phosphorus exhibits allotropic forms: White phosphorus is a white, waxy solid that can be cut with a knife. White phosphorus is toxic, while red phosphorus is nontoxic. Red phosphorous forms when white phosphorous is heated to Kelvin and not exposed to air. Red phosphorus is less reactive than white phosphorus. Phosphorus has many applications: Because it is a metalloid, arsenic has a high density, moderate thermal conductivity, and a limited ability to conduct electricity.
Compounds of arsenic are used in insecticides, weed killers, and alloys. The oxide of arsenic is amphoteric, meaning it can act as both an acid and a base. The chemical formula for this process is given below: Antimony Antimony is also a metalloid. The oxide of antimony is antimony III oxide which is amphoteric, meaning it can act as both an acid and a base. Antimony is obtained mainly from its sulfide ores, and it vaporizes at low temperatures.
Along with arsenic, antimony is commonly used in alloys. Bismuth Bismuth is a metallic element. Bismuth is a poor metal one with significant covalent character that is similar to both arsenic and antimony.
Bismuth is commonly used in cosmetic products and medicine. Out of the group, bismuth has the lowest electronegativity and ionization energywhich means that it is more likely to lose an electron than the rest of the Group 15 elements. This is why bismuth is the most metallic of Group Bismuth is also a poor electrical conductor.
For some atoms, there's actually no attraction for an extra electron. Let's take neon, for example. Neon has an electron configuration of one s two, two s two, and two p six. So there's a total of two plus two plus six, or 10 electrons, and a positive 10 charge in the nucleus for a neutral neon atom. So let's say this is our nucleus here, with a positive 10 charge, 10 protons. And then we have our 10 electrons here, surrounding our nucleus.
So this is our neutral neon atom.
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If we try to add an electron, so here let's add an electron. So we still have our 10 protons in the nucleus. We still have our 10 electrons, which would now be our core electrons. To add a new electron, this would be the neon anion here, so one s two, two s two, two p six. We've filled the second energy level. To add an electron, we must go to a new energy level. So it would be the third energy level, it would be an s orbital, and there would be one electron in that orbital.
So, here is, let's say this is the electron that we just added. So we have to try to add an electron to our neon atom. But if you think about the effective nuclear charge that this electron in magenta feels, alright, so the effective nuclear charge, that's equal to the atomic number, or the number of protons, and from that, you subtract the number of shielding electrons.
Since we have 10 protons in the nucleus, this would be And our shielding electrons would be 10, as well. So those 10 electrons shield this added electron from the full positive 10 charge of the nucleus.
Group General Properties and Reactions - Chemistry LibreTexts
And for a quick calculation, this tells us that the effective nuclear charge is zero. And this is, you know, simplifying things a little bit, but you can think about this outer electron that we tried to add, of not having any attraction for the nucleus. These 10 electrons shield it completely from the positive 10 charge. And since there's no attraction for this electron, energy is not given off in this process.
Actually, it would take energy to force an electron onto neon. So if you wrote something out here, and if we said, alright, I'm trying to go from, I'm trying to add an electron to neon, to turn it into an anion.
Instead of giving off energy, this process would take energy. So we would have to force, we would have to try to force this to occur.
So it takes energy to force an electron on a neutral atom of neon. And we say that neon has no affinity for an electron.
So it's unreactive, it's a noble gas, and this is one way to explain why noble gases are unreactive. This anion that we intended isn't going to stay around for long.
So it takes energy to force this onto our neutral neon atom. So you could say that the electron affinity is positive here, it takes energy. But usually, you don't see positive values for electron affinity, for this sort of situation. At least, most textbooks I've looked at would just say the electron affinity of neon is zero, since I believe it is hard to measure the actual value of this. Here we have the elements in the second period on the periodic table, and let's look at their electron affinities.
We've already seen that adding an electron to a neutral atom of lithium gives off 60 kiloJoules per mol. Next, we have beryllium, with a zero value for the electron affinity.
Electron affinity: period trend (video) | Khan Academy
That means it actually takes energy. So this number is actually positive, and it takes energy to add an electron to a neutral atom of beryllium. So if you think about going from a neutral atom of beryllium to form the beryllium anion, when we look at electron configurations, neutral atom of beryllium is one s two, two s two, and so, to form the negatively charged beryllium anion, it would be one s two, two s two, and to add the extra electron, it must go into a two p orbital, which is of higher energy.
And so, this is actually the same thing, or very similar, to neon, which we just discussed. For neon, the electron configuration was one s two, two s two, two p six, and to add an extra electron, we had to go to the third energy level.
We had to open up a new shell. And the electron that we added was effectively screened from the full nuclear charge by these other electrons. And a similar thing happens here for the beryllium anion. To add this extra electron, we have to open up a higher energy p orbital.
This electron is, on average, further away from the nucleus, and is effectively shielded from the full positive charge of the nucleus, and therefore, there's no affinity for this added electron.
So there's no affinity for this electron, so it takes energy to form the beryllium anion. And that's why we see this zero value here for beryllium. Beryllium has no value for electron affinity, or, it's actually a very positive value, and we just say it has a zero value.
Next, let's look at boron here. So this gives off kiloJoules per mol.
Electron affinity: period trend
And we can see a little bit of a trend here, as we go from boron to carbon to oxygen to fluorine. So as we go across the period on the periodic table, more energy is given off, and therefore, fluorine has the most affinity for an electron.
So as we go across a period, we get an increase in the electron affinity. So the negative sign just means that energy is given off, so we're really just looking at the magnitude. More energy is given off when you add an electron to a neutral atom of fluorine, than if you add an electron to a neutral atom of oxygen. And we can explain this general trend in terms of effective nuclear charge.
As we go across our period, we also have an increase in the effective nuclear charge. And if the added electron is feeling more of a pull from the nucleus, which is what we mean here by increased effective nuclear charge, more energy will be given off when we add that electron.