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

钴是金属元素，子序数是27。

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

而 fiftith 才是序数词的正确写法。

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

给某些事物排序时，那么这时序数词像是第二，第五，作为冠词使。

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

一种元素的子序数是其子核中的质子数。

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

有118种已知的元素，每种元素都是按子序数排列的。

We use ordinal numbers to see which comes first.

我们看是哪个先的时候，使序数。

Finally, you might also hear ordinal numbers used as an adjective.

最后，可能还会听到序数作形容词。

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

但是奥运会上，序数才是最重要的。

This is just waste of space.

而且我们很少会将看起来很累赘的序数直接写日期上。

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子序数有序排列的表。

All of the other ordinal numbers end in a TH.

所有其他以TH结尾的序数词。

Ordinal numbers are numbers that show the order of things.

序数词表示的是事物的顺序。

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

序数代表事物的顺序--想想奥运会获胜者的顺序。

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

序数可以充名词、形容词或副词。

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

这些元素中，哪一个的子序数是六，是已知宇宙中最丰富的元素之一？

With an atomic number of 11, which of these elements gets its symbol from the Latin word " natrium" ?

子序数为11，下面哪个元素的符号来自拉丁词“natrium”？

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

大家会看到数字出现这里，它会是一个序数词。

Ordinal numbers are one important area of grammar that connects with the Olympics.

序数是与奥运会相关的一个重要语法领域。

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

这两个例子中，序数的作都像一个名词。

Ordinal numbers also can act as adverbs.

序数也可以充副词。