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Chinese Muyuan Tian
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周期性
hi it's Paul Andersen and this is chemistry essentials video six is on
大家好，我是Pual Andersen。这是chemistry essential 6. 周期性。
periodicity in other words it's going to be the patterns that we see in the
换句话说，这就是我们看到的元素周期表的形状。
periodic table now what determines that is going to be electron configuration and we can figure that out using the
决定它的就是电子排布。我们可以用aufbau principle来理解。
Aufbau principle which is actually German and it means the principle of building up so we're building up from
这其实是德语，意思是构造的原则。
lower to higher energy levels and so what we can find is these trends that
我门从低能级构筑到高能级，然后我们就能发现其中的规律。
start to emerge but it's most important instead of just memorizing them that you
重要的是你对原子内发生什么的理解而不是仅仅死记硬背。
really understand what's going on inside the atom that determines those those trends and so a periodicity remember is
所以，周期性是基于电子排布之上的。
going to be derived from the electron configuration in other words where the electrons are we can determine that by
就是说电子到底在哪。
using the Aufbau principle and if you
我们可以用aufbau principle去确定。我的上一个关于电子排布的视频对你们很有帮助。
were to watch the last video on electron configuration I think that helped a lot but what's the meaning behind this it
但这背后的意义是什么？
all comes from Coulomb's law which helps to explain electron configuration and
我们可以来看库伦定律，这可以帮助解释电子排布。
also helps explain these trends that explains changes in the ionization energy changes in the atomic and ionic
这还能帮我们解释电离能，原子半径和离子半径的变化。
radii how big the atom or ion is electronegativity and finally the ion
这个原子或者离子到底有多大，电负性亦或者离子电荷。
charge and so if you really understand Coulomb's law you can kind of work your
所以当你完全了解了库伦定律，你就可以了解元素周期表。
way through this on the periodic table why is this important we can use the
为什么元素周期表重要呢？
periodic table to make predictions especially about things that we haven't even designed yet and so if we look at
我们可以用这个来预测，特别是那些我们还没有明确发现的东西。
the periodic table this on the right side is going to show us which of these
来看这张元素周期表，右边这张图展示出了它们背逐渐填满的顺序。
are going to fit be filled over time but if you look at the periodic table we'll
但如果我们看到元素周期表，就可以发现这的规律。
find trends and so here's hydrogen what we really need to do is take helium and
这里是氢。我们把氦放在这里。在s block里。
then put it over in this s block it's going to make us it's a little easier to
这可以让我们好理解一点。
understand and so what we're going to have our energy shells and then these would be sub shells within that and so
这就是我们的能量层，然后这些是是亚电子层，
one thing you should understand about the periodic table is that this F block
还有一件关于周期表的事，f block应该插在这里。
should slide right in here it'd be hard to write a convenient periodic table but that's really how it should be set up
这不是很方便但是的确周期表就是这么组成的。
generally we've just put it down below and so what's guiding this or explaining
一般我们就把它放在下面。
the electron configuration remember is Coulomb's law and so it's pretty simple
库伦定律帮助我们解释电子排布。
if we look at the protons on the inside of the nucleus they have a positive
其实这很简单。如果我们看这些在原子核里的质子，它们有正电荷。
charge the electrons have a negative charge and so Coulomb's law says we just multiplied those in other
这些电子有负电荷。库伦定律的意思是：我们只需要把他们相乘。
words the bigger they are the bigger the force between the two is going to be but
就是说它们越大，它们之间的力就越大。
as we increase the radius the distance between the nucleus and those electrons
但当我们增加半径（质子和电子之间的距离）
then we're going to see a decrease in that force the one thing that you have
我们会发现之间的力变小。另一件事是
to add to that is that once we fill up one of these orbitals or sub shells it's going to shield the electrons on the
当我们填满这些电子轨道，亚电子层时
outside from those on the inside so let's get started and work through this
它们会从外而内把这些电子罩起来。所以我们来看
list what's going to happen to the ionization energy well let's look at
电离能回发生什么呢？我们来看看库伦定律。
Coulomb's law ionization energy is the energy required to pull one of these electrons away and so what's going to
电离能是指电子需要脱离所需的能量。
happen as we increase the size of atoms we're going to increase the number of
所以当原子变大时会发生什么？质子数会变多
protons and so we're going to make it harder for you to pull an electron away
所以我们就更难让一个电子脱离。
and so we move across the periodic table we're going to see an increase in ionization energy what's going to happen
所以我们横向穿过周期表，我们会发现电离能是上升的。
as we go down the periodic table well as
向下会发生什么呢？如果向下，
we go down the periodic table they're getting bigger and bigger and bigger and so the radius is going to get larger and
原子会越来越大，原子半径也会越来越大。
so therefore we're going to see a decrease in ionization energy so you can
所以我们会看到电离能的纵向下降。
think of ionization energy going up and to the right now it's not as simple as
所以我们可以认为电离能是向右向上增长的。但没有那么简单。
this what we're really looking at is within sub shells we're going to see
我们真正要看的是亚电子层和电子轨道
that pattern because you'll see changes within here and orbitals as well but it's just a general trend and it comes
因为我们可以看到这里的变化。但这只是库伦定律的基本趋势。
from Coulomb's law let's look at atomic and ionic radii well what happens as we
我们来看原子和离子的半径。
increase the atomic number we're increasing the number of protons what is
当我们增加原子序数的时候会发生什么？我们会增加质子数。这会怎么样呢？
that going to do it's going to pull it in in other words it's going to pull those electrons more closely to the
它们会拉进来，增加的质子会把电子更加拽向中心。
center and so it's actually going to be
所以其实是相反的。
the opposite it's going to increase as we go down and it's going to increase as we go from the right to the left across
半径会随着周期表的向下移动增加，同时自右向左的移动也会使它增加。
the periodic table and so you can see this graph of atomic radii is actually going to be the inverse of what we saw
所以就想你看到的这幅图一样，原子半径的变化与电离能成反比。
with ionization energy what about electronegativity electronegativity is
那电负性又怎么样呢？
how much an electron and it's bad to say this but wants an electron in other
电负性是一个电子（可能这样有些不妥）渴求一个电子。换句话说
words how much it would like to receive
它多想接受另一个电子。
another electron well remember as we're going across a subshell let's say we're going to classes p-block right here as
我们穿过一个亚电子层，比如这个p block。
we go across we're increasing the number of protons and therefore we're increasing that pull of the nucleus on the electrons outside it and so as we
当我们穿过的时候，我们在增加质子数，所以也增加了质子对电子的拉力。
move from the left to the right we're going to increase how much that
所以当我们从左到右移动时，我们实则在增加原子对电子的需求
Adam wants an electron at least until we get to the noble gases and so
直到惰性气体
electronegativity is going to follow ionization energy as well what if we
所以电负性与电离能是一样的。
look at then ionic charge well to look at ionic charge we really have to look at how close an atom is to a noble gas
我们来看看离子电荷会怎么样。去看离子电荷，我们一定要观察一个原子离惰性气体有多近。
and so let's throw a noble gasses up here noble gases are going to have a
这是惰性气体
full inner electron sub shell and so anything that moves you towards that is going to make you a more stable atom and
惰性气体有全满的亚电子层，所以越靠近它们的会有越稳定的原子结构。
so remember the only atoms that exist by themselves are going to be the noble
所以记住只有惰性气体只以原子它们自己的原子存在。
gases up here so a quick way to figure
一个快速的方式用库伦定律来算出离子电荷的方法是
out ionic charge using Coulomb's law is to just look how close you are to a
就是看它离惰性气体多近。
noble gas and so let's look at the halogens which are right here how many electrons would halogens have to get in order for them to move to a noble gas
我们来看这里的卤族元素。它们需要多少电子来达到惰性气体的状态呢？
well just one electron and so they're going to have in general a negative one
只要一个，所以它们基本上有-1个电荷。
charge let's move over these would have negative two negative three let's go way
向这移，就会有-2，-3.
to the other side with the alkali metals what about them well it would be hard to
从另一边看，像这些碱金属。它们怎么样呢？
go all the way across here to get to the noble gases just easier to go around the
它们不会向这个方向一直移到惰性气体。反而，它们会从背后绕过去。
back in other words they could lose the electron and when you lose the electron
换句话说，它们会丢失电子（来达到稳定状态）。
you have a positive one charge and so we could kind of work it up in this
这样就会有一个正电荷。所以这个方向有时候也是可行的。
direction as well and so again that's it's not hold fast in other words these are general trends but they can all be
重申一遍，这不是一成不变的。换句话说这是普遍的规律。
predicted just by applying Coulomb's law
但是它们都可以被库伦定律预测出来。
so it's hard to talk about the periodic table without talking about Dmitri Mendeleev who's really the father of the
如果提到元素周期表，很难不提到德米特里·门捷列夫，他是元素周期表之父。
periodic table but you've probably never heard of julius von meyer was a german
但是你们应该大都没有听说过 Julius von Meyer，一个德国人
who was working on the periodic table at the same time and published his periodic table around the same time as Mendeleev
他与门捷列夫在几乎同一时间研究并发表了元素周期表。
now why haven't you heard of Meyer well Mendeleev made these huge predictions in
但是为什么你没有听说过呢？原因是门捷列夫做出了大胆的假设。
other words here's his periodic table then you see here that he had some
这是他的周期表。你可以看到这里的问号
question marks where they hadn't identified those atoms what it did is he would predict them and so he predicted
这是他没有辨认或发现的原子。门捷列夫预测了这些原子
germanium and he called it eka silicon
他预测出了germanium（锗）把他称为ekasilicon.
and here all the predictions he made about the properties of this eka silicon and if we look at his predictions and
这里是他对ekasilicon特性的预测，然后我们从上往下
then compare it to the actual values all the way down you'll find that he was pretty much spot-on and that's why
与真实的数据对比，你会发现它们很接近。
Mendeleev is giving credit for the
这就是为什么我们都认为门捷列夫发现了元素周期表
periodic table not only was he able to build it put it to get everybody also made these great predictions and it's predictions were
他不仅仅绘制了这张表，还做出了伟大的预测。
spot-on and so that kind of lends to this next topic I want to talk about
同时这些预测也很精确。这与我下一个想说的材料设计有联系。
which is material design what we can do is we can take things off the periodic
我们可以用周期表里的东西
table so let me grab some atoms let me grab some silicon and some oxygen and so we make some silicon dioxide and when we
我们来拿一些原子。拿一些硅和氧，我们就可以得到一些二氧化硅。
do that we get a ceramic a ceramic is going to be build up maybe stoneware or
这样我们就可以得到一些陶瓷。它们可以被加工为粗陶或瓷器。
earthenware so it's going to build up these tiles over here on the side and so
它们就可被加工成这里的一样的瓦片。
if silicon dioxide can make that well what about something below that what
二氧化硅可以制造这些，那下面的东西可不可以呢？我们来看锡。
about ten if I were to grab that I could say maybe those are going to form
如果我拿出来它们然后假设它们可能被加工成陶瓷。其实事实上它们可以。
ceramics and they will they'll form glazes that are going to be on these ceramic tiles as well and so what scientists can do is they can dance
它们会形成釉，也会出现在陶瓷上。
around the periodic table and if you know some of these trends you can make
科学家可以在元素周期表之间寻找，如果你了解一些规律，你就可以预测新的材料。
predictions about new materials and so
总结一下
again in in summary periodicity comes from the electron configuration which is determined by the Aufbau principle but
周期性源于电子分布，构造原理解释了电子分布。
what really explains it is Coulomb's law which allows us to make these big predictions ionization remember goes up
但事实上，库伦定律才真正解释了周期性。库伦定律让我们有了这些大胆的预测。
and to the right atomic radii increases down into the
记住电离能是向上向右增加的。原子半径是向下向左增加的。
left electronegativity up into the right
电负性向上向右
and then ionic charge remember we find where the noble gases are and then we look at how many electrons we have to gain or lose to get there and then these
然后的电荷数是根据惰性气体的位置决定的。我们找到惰性气体位置，然后决定是要获得或失去多少电子来达到稳定状态。
are important in designing materials so
还有重要的材料设计。
you should have learned to predict or justify transit atomic properties where would I point you if you didn't get that remember looking at this chart and
你应该学会预测或辨认原子的特点。如果不清楚
seeing how ionization and electronegativity change if we look at
看看这张表，电离能和电负性是如何变化的。
justifying the arrangement based on on reactivity it all goes back to Coulomb's
这全部基于库伦定律。
law and remember the bigger the charges are the bigger the ionization energy are the bigger the force holding the electrons in place is going to be
记住电荷越大，电离能越大，电子间的拉力就越大。
there's also the shielding effect and
这是电子层的影响
then remember we can identify patterns to predict design and the example of
记住我们可以确定如何预测材料的特性。
silicon and tin oxides are example of that so that's a periodicity and I hope that was helpful
例子是硅和锡的氧化物。这就是周期性的全部内容。希望能帮到你们。
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