元素週期表....comecome(緊急)

我唔知你form 幾,其實呢個問題係中六,中七先教的,我嘗試解下la(coz i study chem in english, i will use english instead)

in lower form(f4-f5), when we refer to electron shells, we know that:
when n=1, max e-=2
n=2, max e-=8
n=3, max e-=18 etc.
taking example of n=2, it seems that the eight electrons are in the same energy level. however there are presences of subshells showing that the 8 electrons are not in same energy level,
for n=2, it includes 2s orbital and 2p orbital where 2e-in 2s orbital and 6e- in 2p orbitals (in short it can be written as 2s2 2p6)
similarly when n=3, three subshells can be found as 3s2 3p6 3d10
when we determine the electronic configurations of an element, we can use the following laws to help us,

1.hund's law: electron would enter the degenerate(same energy)orbitals before pairing up
2.Aufbau's principle:electrons would enter the orbitals in aascending energy.

from 2, we can know that why potassium is 2,8,8,1 instead of 2,8,9. it is because the 3d orbital is higher energy level than 4s orbital, so outermost e- electron would enter the fourth electron shell/4s orbital.
from your question, Cr(鉻),Cu(銅) are the transition metals (d-block element). transiton metals are differ from those in group 1-3, it is because the electrons start to enter the 3d orbital. As mention before, 4s orbital has lower energy than 3d orbital, we may expect that ,
*electronic configuration of Cr=1s2,2s2 2p6, 3s2 3p6 3d4,4s2 (2,8,12,2)

*remarks: 第1 個no 是electron shell no, 英文字是orbital name,之後個no 是 no of electrons in orbitals
however, this structure is not stable since 4s2 have 2 e-, the repulsions between the paired e- in the 4s orbital outweigh the fact that 4s is higher energy than 3d orbital. on the other hand, Cr would have the following configuration,
electronic configuration of Cr=1s2,2s2 2p6, 3s2 3p6 *3d5,4s1 (2,8,13,1)
*there are totally five 3d orbitals and each orbital can maximumly accommodate 2e-,
as mention before, aufbau's principle suggests that electrons enter the same orbital before pairing up, thereby, in Cr each d orbital has 1 e- so 5 d-orbital have 5 e-. can you notice that the orbitals are half filled? when the orbitals are half filled, it can gain extra stability.
the same argument can be applied to Cu, but this time, its d-orbitals are fully filled. it can gain extra stability as well.
electronic configuration of Cu=1s2,2s2 2p6, 3s2 3p6 3d10,4s1 (2,8,18,1)
instead of 1s2,2s2 2p6, 3s2 3p6 3d9,4s2 (2,8,17,2)

if you are form 4/5 student, it may be a bit hard for you to understand because AL chem is not so easy to follow.my teacher taught this topic for a month since it is a long topic, especially handling the transition element. if you think that my explanation is not enough, you can refer to any AL chemistry textbook(physical chemistry) to learn more.

from 應屆高考生

2007-01-20 20:09:57 補充：
打錯左*there are totally five 3d orbitals and each orbital can maximumly accommodate 2e-,as mention before, aufbau's principle suggests that electrons enter the same orbital before pairing upaufbau's principle 改做hund 's rule

鉻(Cr) 的原子序數是24。





2，8，13，1 係
佢 既
電子在每能級的排布

See:
http://zh.wikipedia.org/wiki/%E9%93%AC

铜(Cu) 的原子序数是29。





2，8，18，1 係
佢 既
電子在每能級的排布

See:
http://zh.wikipedia.org/wiki/%E9%93%9C

I think:
(原子序数 - Atomic No. in the periodic table) and (電子在每能級的排布 - Electrons per shell) are two different (traditional and new) concepts/theory to define an element.
Please check with your text books and your teachers/tutors.
I hope I can help you.

現代元素週期表的形成,主要基於俄國化學家門得列夫和德國化學家梅耶二人當時的工作,他們在幾個月的時間裡,就各自獨立地建立起相似的元素週期表...
不過由於門得列夫首先出版了有關元素週期表的著作,因此人們在提到元素週期表時便都歸功於他...
門得列夫是聖彼得堡大學的化學教授..元素週期表便是他在為學生編寫化學教科書的過程中發展而成...
在編寫時,他把元素性質列在卡片上,將卡片分類時,他注意到...如果把元素按"重量"排列,相似的化學性質經過一定間隔,就會規則地重複出現...
門得列夫即據此建立了元素週期表...
他把元素從左到右按輕至重的順序排成若干橫排,具有相似性質的元素成一直列..

門得列夫的成功,在於他把性質相似的元素排成一列,並且留下一些空缺..他把空缺解釋為尚未發現的元素性質...且還能根據空缺的位置,異常準確地預測尚未發現的元素性質...

早期的元素週期表 是依據-原子量-來排列

是由一位門得列夫所排出來的

而現今你在參考書跟課本看到的

是依據-原子序-來排列的

是後人做修正的

因為在門得列夫那個時期

儀器沒有現在的精準 他就可以排出和現在修正過的很像

所以他的貢獻是很大的


元素週期表









固態
液態
元素週期表
氣態
人造元素

發現者


1
H
氫

原子量 熔點 | 氣化點(C)

2
He
氦



3
Li
鋰


4
Be
鈹

原子殼層 同位素 個

5
B
硼


6
C
碳

7
N
氮
8
O
氧
9
F
氟
10
Ne
氬


11
Na
鈉


12
Mg
鎂

軌道 比重
13
Al
鋁
14
Si
矽
15
P
磷
16
S
硫
17
Cl
氯
18
Ar
氬


圖片參考：http://tw.knowledge.yahoo.com/question/

19
K
鉀

圖片參考：http://tw.knowledge.yahoo.com/question/

20
Ca
鈣


圖片參考：http://tw.knowledge.yahoo.com/question/

21
Sc
鈧


圖片參考：http://tw.knowledge.yahoo.com/question/

22
Ti
鈦

圖片參考：http://tw.knowledge.yahoo.com/question/

23
V
釩

圖片參考：http://tw.knowledge.yahoo.com/question/

24
Cr
鉻

圖片參考：http://tw.knowledge.yahoo.com/question/

25
Mn
錳

圖片參考：http://tw.knowledge.yahoo.com/question/

26
Fe
鐵

圖片參考：http://tw.knowledge.yahoo.com/question/

27
Co
鈷

圖片參考：http://tw.knowledge.yahoo.com/question/

28
Ni
鎳

圖片參考：http://tw.knowledge.yahoo.com/question/

29
Cu
銅

圖片參考：http://tw.knowledge.yahoo.com/question/

30
Zn
鋅

圖片參考：http://tw.knowledge.yahoo.com/question/

31
Ga
鎵

圖片參考：http://tw.knowledge.yahoo.com/question/

32
Ge
鍺

圖片參考：http://tw.knowledge.yahoo.com/question/

33
As
砷

圖片參考：http://tw.knowledge.yahoo.com/question/

34
Se
硒

圖片參考：http://tw.knowledge.yahoo.com/question/

35
Br
溴

圖片參考：http://tw.knowledge.yahoo.com/question/

36
Kr
氪

37
Rb
銣
38
Sr
鍶
39
Y
釔
40
Zr
鋯
41
Nb
鈮

42
Mo
鉬

43
Tc
鎝

44
Ru
釕

45
Rh
銠
46
Pd
鈀
47
Ag
銀
48
Cd
鎘
49
In
錮
50
Sn
錫
51
Sb
銻
52
Te
碲
53
I
碘
54
Xe
氙

55
Cs
銫
56
鋇
57
La
鑭
72
Hf
鉿
73
Ta
鉭
74
W
鎢
75
Re
錸
76
Os
鋨
77
Ir銀
78
Pt
鉑
79
Au
金
80
Hg
汞
81
Tl
鉈
82
Pb
鉛
83
Bi
鉍
84
Po
釙
85
At

86
Rn
氫


87
Fr

88
Ra
鐳
Ac
錒
系
104
Rh
105
Db
106
Sg
107
Bh
108
Hs
109
Mt
110
Uun
111
Uuu
112
Uub
113
Uut
114
Uuq




　
58
鈰
59
鐠
60
釹
61
Pm
62
釤
53
銪
64
釓
65
鋱
66
鏑
67
鈥
68
鉺
69
銩
70
鐿
71
鎦


　
90
釷
91
鏷
92
鈾
93
錼
94
鈽
95
鋂
96
鋦
97
Bk
98
Cf
99
鑀
100
鐨
101
鍆
102
No
103
鐒

的確是要死背
如果是讀高中的自然組 你題目會寫到整張表浮現在你的腦海中
不過國2生應該只需要背元素符號就夠用了
不過現在背起來對將來高中比較有用
我國中時老師發兩張元素週期表的"空格"當考試,一張寫中文.一張寫英文= ="
兩邊最基本的是一定要背的!至於中間的過渡元素,上面一行背一背不會吃虧的~另外再記個Hg.Au.Pt.W.Cd.Ag國中+高中就很夠用了



元素的性質隨著元素的原子序數(即原子核外電子數或核電荷數)的增加呈週期性變化的規律。週期律的發現是化學系統化過程中的一個重要里程碑。

http://hk.knowledge.yahoo.com/question/?qid=7006092205024