Cobalt is a metallic element, atomic number 27 in the period table.

钴是金属元素，原子序是27。

And fiftieth is the correct way to write the ordinal number.

而 fiftith 才是序词的正确写法。

Ordinal numbers are numbers that show the order of things.

序词表示的是事物的顺序。

You'll see a number up here, it'll be an ordinal number.

大家会看到字出现在这里，它会是一个序词。

When you're ordering things, so when ordinal numbers like second, fifth, are used as adjectives.

当你在给某事物排序时，那么这时序词像是第二，第五，作为冠词使用。

An element's atomic number is the number of protons in its nucleus.

一种元素的原子序是其原子核中的质子。

There are 118 known elements, each organized by atomic number.

有118种已知的元素，每种元素都是按原子序排列的。

We use ordinal numbers to see which comes first.

当我们看是哪个先的时候，使用序。

But in the Olympic games, ordinal numbers are of central importance.

但是在奥运会上，序才是最重要的。

This is just waste of space.

而且我们很少会将看起来很累赘的序直接写在日期上。

We have atomic number across the bottom.

我们在底部有原子序。

The periodic table is an organized display of all the chemical elements in order by atomic number.

元素周期表是所有化学元素按原子序有序排列的表。

You can see on the periodic table that's going to be H. It's going 1 atomic number.

您可以在元素周期表中看到 H。它的原子序为 1。

Ordinal numbers suggest an order of things – think the order of winners in the Olympics.

序代表事物的顺序--想想奥运会获胜者的顺序。

Ordinal numbers can act as nouns, adjectives, or adverbs.

序可以充当名词、形容词或副词。

We would find since it has a different atom number it's going to have different ratio of average masses.

我们会发现，由于它的原子序不同，它的平均质量比也不同。

All of the other ordinal numbers end in a TH.

所有其他以TH结尾的序词。

In both cases, the ordinal number is acting like a noun.

在这两个例子中，序的作用都像一个名词。

Ordinal numbers also can act as adverbs.

序也可以充当副词。

Which of these elements, who's atomic number is six is one of the most abundant elements in the known universe?

这元素中，哪一个的原子序是六，是已知宇宙中最丰富的元素之一？