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元素周期表簡介
元素介紹

化學元素周期表（Periodic table of elements）是根據元素原子核電荷數從小至大排序的化學元素列表。列表大體呈長方形，某些元素周期中留有空格，使特性相近的元素歸在同一族中，如堿金屬元素、堿土金屬、鹵族元素、稀有氣體、非金屬元素、過渡元素等。這使周期表中形成元素分區且分有七主族、七副族、Ⅷ族、18族。由于周期表能夠準確地預測各種元素的特性及其之間的關系，因此它在化學及其他科學范疇中被廣泛使用，作為分析化學行為時十分有用的框架。
俄國化學家德米特里·伊萬諾維奇·門捷列夫（Dmitri Mendeleev）于1869年總結發表此周期表（第一代元素周期表），此后不斷有人提出各種類型周期表不下170余種，歸納起來主要有：短式表（以門捷列夫為代表）、長式表（以維爾納式為代表）、特長表（以波爾塔式為代表）；平面螺線表和圓形表（以達姆開夫式為代表）；立體周期表（以萊西的圓錐柱立體表為代表）等眾多類型表。
注：中國教學上長期使用的是長式周期表，即維爾納式為代表。

內容操作
視頻
教程課件
單詞卡片
In this video we'll discuss the periodic table of elements
在本視頻中,我們將討論元素周期表·
A chart called the periodic table of the elements organizes all of the known elements
一張名為元素周期表的圖表組織了所有已知的元素·
Rows in the periodic table are called periods and columns are called groups or families
周期表中的行稱為周期,
and columns are called groups or families
列稱為族或家族·
A section from each of the two bottom periods has been pulled out and placed below the table to avoid making the table too wide
每個底部兩個周期的部分被拉出并放置在表格下方,以避免使表格過寬·
The elements are organized left to right and top to bottom by their atomic number meaning the number of protons in one atom of the element
元素按照它們的原子序數從左到右、從上到下組織,原子序數表示一個元素原子中的質子數·
Each box shows an element represented by its unique symbol
每個框表示一個元素,元素用其獨特的符號表示·
The smaller number next to each element's symbol represents the atomic number
每個元素符號旁邊的較小數字代表原子序數·
The atomic number increases by one as you go from left to right across each period
原子序數從左到右依次遞增·
The larger number represents the atomic mass
較大的數字表示原子質量·
Notice that the atomic mass of many elements is a decimal number rather than a whole number
注意,許多元素的原子質量是小數而非整數·
This is because the atomic mass is a weighted average of the mass numbers for the isotopes of an element
這是因為原子質量是該元素同位素質量數的加權平均值·
A weighted average takes into account how common each isotope of an element is in nature
加權平均考慮了元素各同位素在自然界中的常見程度·
The most common isotope counts for much more in the average than less common isotopes
最常見的同位素在平均值中的權重遠大于不太常見的同位素,
just like a final exam may count more than quizzes towards your grade in a class
就像期末考試可能比小測驗在課堂成績中占更大比重一樣·
Notice that the atomic mass isn't the same as mass number
注意,原子質量不同于質量數,
which is simply the total number of protons and neutrons in the nucleus of a particular isotope
質量數是指特定同位素原子核中質子和中子的總數·
However you can determine the mass number of an element's most common isotope by rounding its atomic mass up or down to the nearest whole number
然而,你可以通過將元素的原子質量四舍五入到最接近的整數來確定該元素最常見同位素的質量數·
You can do this because the most common isotope has the most influence on the atomic mass
你可以這樣做,因為最常見的同位素對原子質量的影響最大·
Round up if an element's atomic mass ends in 5 or greater round down if an element's atomic mass ends in less than 5
如果元素的原子質量末尾是0.5或更大,則四舍五入到上一個整數;如果末尾小于0.5,則四舍五入到下一個整數·
Let's look at some examples from the periodic table
讓我們看一些周期表中的例子·
Helium has an atomic mass of 4 003
氦的原子質量為4.003·
We can easily round that down to get a mass number of 4
我們可以輕松地將其四舍五入得到質量數4·
We can also see that helium's atomic number is 2 which means it has 2 protons
我們還可以看到氦的原子序數是2,這意味著它有2個質子·
Now we can subtract the atomic number from the mass number to see that the most common isotope of helium has 2 neutrons
現在,我們可以從質量數中減去原子序數,看到氦的最常見同位素有2個中子·
In the case of oxygen we can round its atomic mass up to get a mass number of 16
對于氧氣,我們可以將其原子質量四舍五入得到質量數16·
Since its atomic number is 8 we know oxygen has 8 protons
由于它的原子序數是8,我們知道氧氣有8個質子·
And by simple subtraction we can determine oxygen also has 8 neutrons
通過簡單的減法,我們可以確定氧氣也有8個中子·
How does this work in a less common isotope of an element such as hydrogen 3
這種方法在元素的不太常見同位素中如何運作呢?比如氫-3?
The most common hydrogen isotope is hydrogen 1
氫的最常見同位素是氫-1,
as you can see from rounding the atomic mass listed in the periodic table
正如你可以從周期表中列出的原子質量四舍五入看到的·
Recall that isotopes are identified by their mass number
記住,同位素是通過它們的質量數來識別的·
So we know hydrogen 3's mass number is 3
因此,我們知道氫-3的質量數是3·
So we can subtract hydrogen's atomic number of 1 from its mass number and see that hydrogen 3 has 2 neutrons
因此,我們可以從氫的原子序數1中減去質量數,看到氫-3有2個中子·
In summary the periodic table is an organization chart of all the known elements
總結一下,周期表是所有已知元素的組織圖表·
Each element is represented by its symbol atomic number and atomic mass
每個元素由其符號、原子序數和原子質量表示·
Elements are arranged left to right and top to bottom by increasing atomic number
元素按照原子序數從左到右、從上到下排列·
An element's atomic mass is a weighted average of its isotope's mass numbers
元素的原子質量是其同位素質量數的加權平均值·
Round the element's atomic mass up or down to find the mass number of its most common isotope
將元素的原子質量四舍五入,以找到其最常見同位素的質量數·