# The graph represents relationship between atomic radii

### Atomic radius trends on periodic table (video) | Khan Academy Within a row of the periodic table, the electronegativity tends to increase with Which of the following graphs best represents the relationship between atomic. Predict whether the arsenic ion shown in the graph has a positive or Describe the relationship between atomic radii and number of the transition Which of the following electron configuration represents the most chemically stable atom. Which electron configuration represents an atom Compared to the radius of a chlorine atom, the radius of a The graph below represents the relationship. And you might say, "well okay, that's easy to figure out the atomic radius. I just figure out the distance between the nucleus and the outermost electron and we could call that the radius. Electrons are not in orbits the way that planets are in orbit around the sun and we've talked about this in previous videos.

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They are in orbitals which are really just probability distributions of where the electrons can be, but they're not that well defined. So, you might have an orbital, and I'm just showing you in 2 dimensions.

It would actually be in 3 dimensions, where maybe there's a high probability that the electrons where I'm drawing it in kind of this more shaded in green. But there's some probability that the electrons are in this area right over here and some probability that the electrons are in this area over here, and let's say even a lower probability that the electrons are over this, like this over here.

And so you might say, well at a moment the electron's there. The outermost electron we'd say is there. You might say well that's the radius. But in the next moment, there's some probability it might be likely that it ends up here. But there's some probability that it's going to be over there. Then the radius could be there. So electrons, these orbitals, these diffuse probability distributions, they don't have a hard edge, so how can you say what the size of an atom actually is?

There's several techniques for thinking about this. One technique for thinking about this is saying, okay, if you have 2 of the same atom, that are- 2 atoms of the same element that are not connected to each other, that are not bonded to each other, that are not part of the same molecule, and you were able to determine somehow the closest that you could get them to each other without them bonding. So, you would kind of see, what's the closest that they can, they can kind of get to each other? So let's say that's one of them and then this is the other one right over here. And if you could figure out that distance, that closest, that minimum distance, without some type of, you know, really, I guess, strong influence happening here, but just the minimum distance that you might see between these 2 and then you could take half of that. So that's one notion.

That's actually called the Van der Waals radius. Another way is well what about if you have 2 atoms, 2 atoms of the same element that are bonded to each other? They're bonded to each other through a covalent bond. So a covalent bond, we've already- we've seen this in the past. The most famous of covalent bonds is well, a covalent bond you essentially have 2 atoms. So that's the nucleus of one. That's the nucleus of the other. And they're sharing electrons. So their electron clouds actually, their electron clouds actually overlap with each other, actually overlap with each other so the covalent bond, there the electrons in that bond could spend some of their time on this atom and some of their time on this atom right over here.

And so when you have a covalent bond like this, you can then find the distance between the 2 nuclei and take half of that and call that call that the atomic radius. So these are all different ways of thinking about it. The atomic radius, in picometers, is given below the sphere that represents the atom. The fuzziness of the edges of the spheres is meant to imply the uncertainty inherent in discussions of the size of an atom.

Figure 1 Atomic Radii as a Function of Atomic Number Before we consider the data in Figure 1, you may want to review your knowledge of the periodic table. Exercise 2 Across a given row of the periodic table, the general trend is that the radii of the atoms decrease as their atomic numbers. Such a relationship between atomic number and atomic radius is a direct correlation. According to Coulomb's Law, as the atomic number increases within a series of atoms, the nuclear attraction for electrons will also increase, thus pulling the electron s closer to the nucleus.

The Coulombic attraction of the nucleus of an atom for its electrons is referred to as the electronegativity of the atom. Exercise 3 Within a given group column of the periodic table, the general trend is that the radii of the atoms increase as their atomic numbers.

At this point we have an apparent dichotomy. On the one hand there is a direct correlation between atomic size and atomic number, while on the other there is an inverse correlation between these two variables. Whenever you encounter a situation like this, you may be certain that there is another variable at play.

You need more data. So let's look at Ionization Energies The ionization energy of an atom is the amount of energy required to separate an electron from the neutral atom.

It is the energy needed to overcome the force of attaction, Fc, between the nucleus and the electron that is farthest from it.

Equation 1 depicts the process in general terms. Figure 2 presents a plot of ionization energies as a function of atomic number for the same elements shown in Figure 1. Across a given row of the periodic table, the general trend is that the ionization energies of the atoms increase as their atomic numbers.

Such a correlation between atomic number and ionization energy is direct inverse. Exercise 5 Complete the following statement: Within a given group column of the periodic table, the general trend is that the ionization energies of the atoms decrease as their atomic numbers. Let's think about what's involved in the measurement of the ionization energy of an atom. This can similarly be said about the protons pulling the electrons closer to the nucleus, which as a result decreases atomic size.

The ionic radius decreases for the generation of positive ions. This can be seen in the Figure 4 below. The gain of an electron adds more electrons to the outermost shell which increases the radius because there are now more electrons further away from the nucleus and there are more electrons to pull towards the nucleus so the pull becomes slightly weaker than of the neutral atom and causes an increase in atomic radius.

The ionic radius increases for the generation of negative ions. Metallic Radius The metallic radius is the radius of an atom joined by metallic bond. The metallic radius is half of the total distance between the nuclei of two adjacent atoms in a metallic cluster.

Metallic radii from metallic bonding Periodic Trends of Atomic Radius An atom gets larger as the number of electronic shells increase; therefore the radius of atoms increases as you go down a certain group in the periodic table of elements.

Periodic Trend in atomic radii Vertical Trend The radius of atoms increases as you go down a certain group. Because the electrons added in the transition elements are added in the inner electron shell and at the same time, the outer shell remains constant, the nucleus attracts the electrons inward.

The electron configuration of the transition metals explains this phenomenon. This is why Ga is the same size as its preceding atom and why Sb is slightly bigger than Sn. Herring, and Jeffry D. Pearsin Prentice Hall, Problems Which atom is larger: Which atom is larger: Which atom is smaller: Put in order of largest to smallest: