Electron Affinity: Definition, Trends & Equation - Video & Lesson Transcript | balamut.info
What is the relationship between atomic radius, ionic radius, ionization energy, and electron affinity? Are atomic and ionic radius related and. Periodic trends are specific patterns in the properties of chemical elements that are revealed in the periodic table of elements. Major periodic trends include electronegativity, ionization energy, electron affinity, atomic radius, ionic radius, metallic character, and chemical. Generally speaking, there is a negative correlation between atomic radius and electron affinity. There are exceptions (aren't there always), but.
And this electron, we know, is shielded from the full positive three charge of the nucleus by our two core electrons in here, right? So like charges repel. It's also going to be repelled a little bit by this electron, that's also in the two s orbital. So this electron's going to repel this one as well. But, there is an attractive force between our positively charged nucleus and our negative charge on the electron.
AK LECTURES - Atomic Radius, Ionization Energy, Electronegativity and Electron Affinity
So this electron that we added still feels an attractive force that's pulling on it from the nucleus. And so, if you add this fourth electron, energy is given off. And since energy is given off, this is going to have a negative value for the electron affinity. For adding an electron to a neutral lithium atom, it turns out to be kiloJoules per mol.
So energy is released when an electron is added, and that is because the electron that we added is still able to be attracted to the charged nucleus. So if the nucleus has an attraction for the added electron, you're going to get a negative value for the electron affinity. Or that's one way to measure electron affinity. Note that the lithium anion is larger than the neutral lithium atom. It's just hard to represent it here with those diagrams.
So as long as the added electron feels an attractive force from the nucleus, energy is given off. Let's look at one more comparison between ionization energy and electron affinity.
In ionization energy, since the outer electron here is attracted to the nucleus, we have to work hard to pull that electron away.Ionization Energy Electron Affinity Atomic Radius Ionic Radii Electronegativity Metallic Character
It takes energy for us to rip away that electron. And since it takes us energy, we have to do work, and the energy is positive, in terms of ionization energy. But for electron affinity, since the electron that we're adding is attracted to the positive charge of the nucleus, we don't have to force this, we don't have to do any work.
Energy is given off in this process, and that's why it's a negative value for the electron affinity. Electron affinities don't have to be negative. 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. 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. 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.
Electron affinity: period trend
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. That means it actually takes energy. Nissa Garcia Nissa has a masters degree in chemistry and has taught high school science and college level chemistry. When an electron is added to an atom, a change in energy occurs. This change in energy is what we call the electron affinity.
In this lesson, we will discuss electron affinity and its general trend in the periodic table. What is Electron Affinity? Imagine you're carrying a bag and adding things to it. Naturally, the bag becomes heavier, and there is a change in the energy you expend when the weight changes.
In the same way, when an atom gains electrons, an energy change occurs. This energy change is what we call the electron affinity. The electron affinity is defined as the energy change that occurs when an atom gains an electron, releasing energy in the process. Let's remember that an electron is negatively charged, so when an atom gains an electron, it becomes a negative ion.
Since we are talking about a change in energy, when an electron is added to an atom, there is an equation used to determine the electron affinity: This equation shows that electron affinity is equal to the negative change in energy. Let's clarify the sign convention for the energy change associated with the gain of an electron.
Remember that the definition of an electron affinity is the energy released, so that means that the reaction is exothermic. If a reaction is exothermic, the change in energy is negative.
This means that the electron affinity is positive. For example, the electron affinity of chlorine has the negative sign, which shows us the energy that is released to add one electron to an atom. The giving off of energy is shown with a negative sign. Based on this sign convention, this means that a higher electron affinity indicates that an atom more easily accepts electrons. A lower electron affinity indicates that an atom does not accept electrons as easily.