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原子有多小

How Small is an Atom?

《杰瑞德欧文》
What’s the smallest thing you can think of?
你能想到最小的东西是什么?
Maybe a penny or a button?
也许是一美分硬币或一颗纽扣?
How about a cheerio?
又或是一粒麦圈?
Its height is about half of a Centimeter.
一粒麦圈大约半厘米高
For comparison, there are 100 Centimeters in a Meter.
为便于比较 一米等于一百厘米
Let’s go smaller, a grain of salt,
让我们看看更小的 一粒盐
this is about 0.3 Millimeters.
一粒盐大约是0.3毫米
There are 1,000 Millimeters in a Meter.
一米等于一千毫米
And even smaller…
再看看更小的
Bacteria are only a few Micrometers.
细菌只有几微米
There are 1 million Micrometers in a Meter.
一米等于一百万微米
A virus is about 20 to 300 Nanometers.
一个病毒大约是20到300纳米
There are 1 Billion Nanometers in a Meter.
一米等于十亿纳米
The diameter of DNA is about 2 Nanometers.
DNA的直径约为2纳米
The size of an Atom is only a few Angstroms.
一个原子只有大约几埃米
There are 10 billion Angstroms in 1 Meter.
一米等于一百亿埃米
When you think of an atom,
当你想到原子
you probably picture something like this –
你脑中可能出现如下画面
on the outside – you’ve got electrons that have a negative charge;
在外层 是带着负电荷的电子
in the middle is the nucleus.
中间是原子核
It’s made of neutrons, which have no charge,
由不带电荷的中子
and protons, which have a positive charge.
以及带正电荷的质子组成
This model is a good starting point, but there are
这个模型是个很好的开端
a few things here that don’t quite agree with modern science.
但其中有一些内容 不太符合现代科学
For one, the size of the nucleus is a lot smaller than this.
例如 实际的原子核远远小于模型所展现的
If I animate it to scale,
如果按真实比例绘制
you wouldn’t even be able to see it.
你甚至看不到它
The same thing with these electrons.
电子也是一样的情况
An other thing that’s inaccurate,
另一件不精准的事
is that electrons orbit the nucleus;
就是电子绕原子核轨道运行
just like a planet orbits a star.
就像行星围绕恒星运行一样
Unfortunately, this is still taught in many textbooks,
不幸的是 许多教材依然是这么教的
but it’s just not correct.
但是这是不正确的
Let me cover some background first.
首先让我普及一下背景知识
Over 2,000 years ago
在2000多年以前
ancient Greek philosophers had this idea that
古希腊哲学家认为
everything was made of tiny particles;
万物都由微小粒子构成
they called these tiny particles atoms.
他们称这些微粒为原子
It wasn’t until the 1800s, that we finally started using science to prove
直到19世纪 我们才开始用科学去证实
that these atoms really exist.
原子是真实存在的
First we thought atoms looked like this;
起初我们认为原子是这样的
a positively charged sphere with negatively charged
一个带正电荷的球体
electrons floating around it.
周围漂浮着带负电荷的电子
Then we learned that this positively charged sphere
后来我们意识到 这个带正电荷的球体
was actually a lot smaller;
实际上要小很多
we called this the nucleus.
我们称它为原子核
Slowly but surely, we learned that the nucleus
虽然缓慢但毫无疑问的 我们认识到
is made up of protons and neutrons.
原子核是由质子和中子构成
These electrons were tricky.
这些电子很狡猾
At first we thought, they have to be doing something,
最开始我们认为它们一定是在做某些事情
so they probably revolve around the nucleus like this.
所以它们大概是这样围绕着原子核转动
Electrons were then discovered to have different energy levels
后来的研究发现电子具有不同的能级
we call these shells.
我们称之为壳层
Shells can only fit a certain amount of electrons;
壳层里只能容纳一定数量的电子
the more electrons, the more shells.
电子越多 壳层越多
It didn’t take long before we realized that
很快我们便意识到
these shells don’t determine how close the electron is to the nucleus.
这些壳层并不能决定 电子与原子核间的距离
As it turns out, electrons are a lot more unpredictable.
事实证明 电子更加变化莫测
So if electrons don’t orbit the nucleus…
那么如果电子不再围绕原子核运动
what do they do?
它们会做什么呢?
Let’s start with an idea of an orbit.
让我们从轨道的概念开始
Here we have the Earth going around the Sun.
这是地球围绕着太阳转
If the Earth is here today,
如果地球今天在这个位置
we can use the laws of physics and gravity
我们可以利用物理定理和地心引力
to predict exactly where the Earth will be
预测三个月后
three months from now.
地球的确切位置
We know both where the Earth is and where it’s going.
我们知道地球的位置及地球将运行到哪里
Now let’s go to the size of an atom.
现在让我们来看看原子
With an electron, things are a little different.
电子的情况略有不同
We can’t know exactly where it is and where it’s going.
我们不知道电子的确切位置以及它将去哪
We can only know one or the other at any given time.
我们在任何时候都只能知道电子的一个位置
This means it is impossible to really
这就意味着
know what the electron is doing.
我们不可能真正知道电子在做什么
The best we can do
我们最多能做到
is predict where the electron will be found.
预测电子将会在哪里被发现
This area is most commonly known as the Electron Cloud.
这个区域 通常被称为电子云
However, if we want to be more specific about where
然而 如果想更精确地找到电子
to find electrons, you’ll need to know about orbitals.
你需要了解轨态
This is not the same as orbit.
轨态和轨道不同
Orbitals are specific shapes where electrons live in.
轨态是电子所在之处特定形状的空间
If you were in a College chemistry class,
如果你在上大学的化学课
you’d be studying about how these orbitals fill up
你会学习到当电子越来越多的时候
as you get more electrons.
这些轨态是如何被填满的
But… I’d like to keep things simple for this video.
但是 我想让这个视频里的内容简单一些
So in short,
所以简而言之
electrons are uncertain,
电子具有不确定性
we can’t know the path that they travel;
我们不知道它们的活动路径
only that they will be found here, in the electron cloud.
只有在电子云中才能找到它们
So now you know, that even though this is a popular way to represent an atom
所以现在你知道 尽管这是展现原子的流行方式
it can be misleading.
但这个模型具有误导性
Just to recap what we learned…
回顾一下我们所学到的
Everything is made of atoms.
所有物体都由原子构成
Atoms are incredibly small.
原子非常小
The nucleus is even smaller.
原子核更小
And electrons don’t orbit the nucleus,
电子不是绕着原子核按轨道活动
their path is unpredictable.
电子的运动路径是不可预测的
Thanks for watching everyone,
感谢大家的观看
my name is Jared Owen, and I’ll see you next time.
我是杰瑞德·欧文 下次再见

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视频概述

原子有多小?电子又是如何围绕原子运动?欢迎在本期视频中寻找答案!

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视频来源

https://www.youtube.com/watch?v=ukGLH_NrFH8

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