compound係唔係只有2個molecule~唔會有3個

我諗你搞錯野ｄ野先ｌａ
首先乜野係molecules la?
比如說你有一個NaCl la~
咁即係你有一粒sodium chloride 的molecule
跟住...乜野係compound la?
compound係即係化合物
由離子(ion)或者由兩粒或以上的atom共同分享電子(electron)所組成
如果你條問題係問
compound係唔係只有2個atom/ions?唔會有3個la?
咁個答案其實係唔係ge~
比如說iron(III) hydroxide
佢個chemical formula就係Fe(OH)3
即係由一粒iron(III) ion同3粒hydroxide ions所組成的compound
又比如說我地最常見的水(H2O)
就係由2粒hydrogen同一粒oxygen share electrons去姐成的
所以係唔只由2粒atom/ions去組成ge~
點解有d compound會咁la?
首先我要講因為每一種element(元素)有唔同ge electronic arrange(電子排列)
當中以最外層有8粒eletrons為最穩定
基本上除左group 0的element(noble gases)
所以的element通常都會是不隱定的
為左令自穩定D...佢地就會放出ELECTRON
唔同element會有唔同數目的electrons響outermost electron shell
比如groupI會有1粒,group 2會有2粒,group會有3粒
ｅ１ｄ外層電子數量比較少ｇｅ　element會放較鐘意甩電子去變成正離子(cation)
反之外層電子數量比較多ge element
好似groupVII同group VI的element,佢地就會鐘意接收電子去變成負離子(anion)
無論有甩電子定係接收電子都好
佢地ge目的都係為左令自己穩定!
好la咁element甩左ge電子會去左邊la?
答案就係去左要接收電子ge element倒~
咁一粒group III ge element(例如aluminium)甩左3粒電子la
咁咁o岩接收電子ge 係groupVII ge element
咁每粒group VII ge element(例如chlorine)只可以接收一粒電子
一粒chlorine係唔夠接收晒3粒aluminium ge 3粒電子
所以就會1粒aluminium同3粒chlorine去from compound
即係AlCl3
至於share eletrons ge compound
比較麻煩通常會畫圖先講得明
容許我唔講la~

2007-02-21 16:44:02 補充：
你係唔係問緊由兩個compound做成ge?但係會有ｄ咁樣樣ｇｅ　ｃｏｍｐｏｕｎｄK2Cr2O7或者 K2MnO4ed咁 compound就咁睇落去...好似係有3種唔同ion...其實只係兩種你應該有聽過sulphate ion SO4 2-或者cardonate ion CO3 2-果d叫做polyatomic ion有時會有d咁ge情況佢地極其量會有一d由兩隻由covalent compound ge ion組成但係唔會有兩個ionic compound ge ion組成ge compound law如果你唔明再問la我再答-v-

AlCl3 is not an ionic compound.
Instead, it is a covalent compound.

I know this sounds weird,
but do take a look at this.
http://en.wikipedia.org/wiki/Aluminium_chloride
you will see :P

Good interpretation by the way :D

i think you have mixed up atom and molecule.
those called atom is the basic form of element
like Na K Ca O N
those called molecules is the compound formed by non-metals
like N2 O2

stick to your question
compound surely can be formed by 3 or more kinds of atoms
like ionic compound K2MnO4 it consists 3 kinds of atoms
K Mn and O

NaCl 是compound, 由Na 和 Cl 兩個atom組成, 不是molecule.
總之兩個atom以上組成的都叫compound
molecule是一種compound, 如CO2, O2, N2, 都是molecule, 因為這些都是有covalent bond在中間!