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So would you expect, therefore, as we go across a row for the atomic radius, to increase or to decrease? Good. OK, yes.
那么大家觉得，原子半径沿着某一行向右走，是会增大还是会减小呢？很好，不错，是的。
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We'll then take a turn to talking about the periodic table, we'll look at a bunch of periodic trends, including ionization energy, electron affinity, electronegativity and atomic radius.
然后我们再开始讲元素周期表，我们会看到很多周期性规律，比如电离能，电子亲和能，电负性以及原子半径。
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Here is atomic radius versus atomic number.
这是原子半径和原子序数。
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We talked about ionization energy, electron affinity, we talked about electronegativity, which is just kind of a combination of the first two, and then ended with atomic radius here.
我们讲了电离能的，电子亲和能的，还讲了电负性的，也就是前两个的组合，最后讲了原子半径的。
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So we haven't gotten to molecules yet, we're just talking about single atoms or single ions, but what's nice is just talking about this very straightforward principle of atomic radius.
我们还没有开始讲分子，我们仍然只是在讨论单个原子或离子，但它的好处在于可以讨论,这个关于原子半径的非常简单直接的原理。
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And all ion channels are selective for a single type of ion, and we can think about how that selectivity takes place, and that's where this idea of atomic radius is going to become very important.
所有的离子通道都是仅对某一种离子具有选择性的，而我们可以来想一想这种选择性是如何发生的，这也就是原子半径这个概念将会变得，非常重要的地方。
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So as we go down we're now adding electrons to further and further away shells, so what we're going to see is that the atomic radius is going to increase as we're going down the periodic table.
当我们向下走时,我们会将电子加在越来越远的壳层上，因此我们将看到原子半径,将随我们沿周期表向下走而增大。
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All right, so now we can move on to the start of today's notes, which is atomic radius.
好，现在我们可以开始讨论今天的讲义了，从原子半径开始。
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So, keep that in mind when we're talking about atomic radius, I'm not suddenly changing my story and saying, yes, we do have a distinct radius.
因此，当我们讨论原子半径的时候要时刻记住这一点，我并不是在突然改变自己的说法，说是的，我们的确有一个准确的半径。
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Whereas, if we go across a row, what we see is that the atomic radius is decreasing.
然而如果我们沿着行来看，我们会看到原子半径在逐渐减小。
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And if we're talking about atomic radius, essentially we're talking about atomic size.
如果我们在讨论原子半径，实际上我们讨论的是原子的尺寸。
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And first, on your lecture notes, I start with atomic radius.
首先，在大家的讲义上，我是从原子半径开始的。
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This includes atomic radius and the idea of isoelectronic atoms.
包括原子半径,以及等电子原子的概念。
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You just need to remember what's happening to z effective, which really tells us what's happening with all the trends, and once you know z effective, you can figure out, for example, what direction the atomic radius should be going into.
你只需要记住有效核电量的规律，实际上它会告诉我们所有的规律，只要你知道了有效核电量的规律，你就可以判断，比如，原子半径会向着哪个方向发展。
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And what we've been talking about with all of these properties are, of course, how can we figure out what that is for a certain atom by looking at the periodic table, so we want to think about the periodic trend for atomic radius.
对于我们讲过的这些性质，我们所讨论的一直都是,当然是，我们如何能够判断某一个原子的这些性质,通过观察周期表，因此我们需要思考一下原子半径的周期性规律。
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And immediately it should probably come into your head that we don't actually have an atomic radius that we can talk about, right?
一提到这点你就应该立刻想到,我们并没有一个真正的原子半径,可以讨论，对吗？
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So, these are two different definitions of how to think about atomic radius, but really what you find when these are measured is they come up with almost the identical values, so there are tables, you can look up of atomic radii and see these values, and you can trust them that, they work for both this definition and for this definition here, in most cases.
这就是,关于原子半径的两种不同的定义，但实际上你会发现按照这两种方法,测量出的值是相等的，因此有很多关于原子半径的表格，你可以通过查阅它找到这些值，你可以相信这些值，它们对于这两种定义都是适用的，在大多数情况下。
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that's one way to think about it, and there's also another way, and this is the way that your book presents it. If you, in fact, have two of the same atom right next to each other, let's say you have a crystal, or let's say you're talking about a metal, what you can do is just look at the distance between the two nuclei, and split that in 1/2, and take the atomic radius that way.
这只是一种定义的思路，另外还有其它方法，也就是你们课本上的方法，如果你，事实上，有两个相同的原子彼此靠在一起，比如说你有一个晶体，或者说你讨论的是一个金属，你所要做的就是,看看这两个原子核之间的距离，然后将距离除以二，就得到了这个原子的半径。
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In other words, just want to know where the electron is somewhere within the shell radius of the ground state of atomic hydrogen anywhere.
换言之，我只是想知道,电子在哪,可以在氢原子基态下的半径,里面的任何地方。
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It is the value of the radius of the ground state electron orbit in atomic hydrogen.
它就代表氢原子基态电子,的轨道半径。
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What you see is that the radius changes with atomic number for constant electron number.
对于等电子数的粒子，离子半径随着,原子数的变化而变化。
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