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元素周期表簡(jiǎn)介
元素介紹

化學(xué)元素（Chemical element）就是具有相同的核電荷數(shù)（核內(nèi)質(zhì)子數(shù)）的一類原子的總稱，從哲學(xué)角度解析，元素是原子的質(zhì)子數(shù)目發(fā)生量變而導(dǎo)致質(zhì)變的結(jié)果。
常見元素有氫，氧，氮和碳等。2019年為止，共有118種元素被發(fā)現(xiàn)，其中94種存在于地球上。擁有原子序數(shù)≥83（鉍元素及其后）的元素的原子核都不穩(wěn)定，會(huì)發(fā)生衰變。第43和第61種元素（锝和钷）沒有穩(wěn)定的同位素，會(huì)進(jìn)行衰變。自然界現(xiàn)存最重的元素是94號(hào)钚。

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What is an element
元素是什么?
Elements are pure substances that are made up of only one type of atom such as hydrogen carbon or mercury
元素是由僅一種類型的原子組成的純物質(zhì),如氫、碳或汞·
So what makes one element different from another
那么,是什么使得不同的元素彼此不同呢?
Well it's the number of protons in a single atom of an element
它們的區(qū)別在于每個(gè)元素的原子中質(zhì)子的數(shù)量·
This is called the element's atomic number
這個(gè)數(shù)字叫做元素的原子序數(shù)·
For example hydrogen has one proton in its nucleus so its atomic number is one
例如,氫的原子核中有一個(gè)質(zhì)子,所以它的原子序數(shù)是1·
Carbon has six protons so its atomic number is six
碳有六個(gè)質(zhì)子,所以它的原子序數(shù)是6·
And mercury's atomic number is 80 because it has 80 protons in its nucleus
汞的原子序數(shù)是80,因?yàn)樗脑雍酥杏?0個(gè)質(zhì)子·
Since the nucleus contains almost the entire mass of an atom the number of particles it contains has a big effect on the atom's mass
由于原子核幾乎包含了原子的大部分質(zhì)量,因此它所包含的粒子數(shù)量對(duì)原子的質(zhì)量有很大的影響·
Each positively charged proton has a mass unit of one and each neutral neutron also has a mass unit of one
每個(gè)帶正電的質(zhì)子質(zhì)量單位為1,每個(gè)中性中子的質(zhì)量單位也為1·
The total number of protons and neutrons in the nucleus of an atom is called the mass number
原子核中質(zhì)子和中子的總數(shù)稱為質(zhì)量數(shù)·
In this example the mass number of a hydrogen atom is one
在這個(gè)例子中,氫原子的質(zhì)量數(shù)是1·
Hydrogen is the only element that usually doesn't have any neutrons
氫是唯一通常沒有中子的元素·
The mass number of this carbon atom with six protons and six neutrons is 12
這個(gè)碳原子的質(zhì)量數(shù)是12,因?yàn)樗辛鶄€(gè)質(zhì)子和六個(gè)中子·
And the mass number of this mercury atom with 80 protons and 121 neutrons is 201
這個(gè)汞原子的質(zhì)量數(shù)是201,因?yàn)樗?0個(gè)質(zhì)子和121個(gè)中子·
Needless to say mercury is a much heavier element than hydrogen or carbon
不用說(shuō),汞是比氫或碳重得多的元素·
Even though every atom of the same element always has the same number of protons sometimes an element has atoms with different numbers of neutrons
盡管同一種元素的每個(gè)原子總是有相同數(shù)量的質(zhì)子,但有時(shí)元素的原子會(huì)有不同數(shù)量的中子·
Ordinary hydrogen has no neutrons but there's a version of hydrogen with one neutron and another version with two neutrons
普通氫沒有中子,但氫有一種含一個(gè)中子的版本,還有一種含兩個(gè)中子的版本·
Atoms of the same element with different numbers of neutrons are called isotopes
具有不同中子數(shù)的同一元素的原子叫做同位素·
The three isotopes you see here are all still hydrogen because they all have only one proton
這里看到的三種同位素仍然是氫,因?yàn)樗鼈兌加星抑挥幸粋€(gè)質(zhì)子·
Since neutrons have about the same mass as protons isotopes of the same element have different mass numbers
由于中子的質(zhì)量與質(zhì)子相近,因此同一元素的同位素具有不同的質(zhì)量數(shù)·
In fact an element's isotopes are often identified by their mass numbers
事實(shí)上,元素的同位素通常通過(guò)它們的質(zhì)量數(shù)來(lái)識(shí)別·
To sum up an element is a pure substance made of atoms that always have the same number of protons
總之,元素是由原子組成的純物質(zhì),這些原子的質(zhì)子數(shù)量總是相同的·
This means atoms with different numbers of protons are different elements
這意味著具有不同數(shù)量質(zhì)子的原子是不同的元素·
The number of protons in one atom of an element is called the atomic number
一個(gè)元素的原子中質(zhì)子的數(shù)量稱為原子序數(shù)·
The number of protons plus neutrons in one atom is called the mass number
一個(gè)原子中質(zhì)子加中子的數(shù)量稱為質(zhì)量數(shù)·
Isotopes are atoms of the same element with different numbers of neutrons
同位素是具有不同數(shù)量中子的同一元素的原子·