我唔係好明D科學家點解可以知道有proton,neutron

electron
Acient Greek found that amber (虎珀) attracted things after rubbing with fur and call this electric

1876, Eugan Goldstein discovered that a beam of rays come out fro the negative electrod(cathode) adn hit the positive electrode(pict.1)

pict.1


圖片參考：http://www.hcc.mnscu.edu/chem/V.08/Gas_Discharge_Tube.jpg

pict.2

圖片參考：http://www.hcc.mnscu.edu/chem/V.08/DT_and_Mag_field.jpg

pict.3

圖片參考：http://www.hcc.mnscu.edu/chem/V.08/DT_and_electric_field.jpg
1897, J.J. Thomson found that cathode rays were deflected in a magnetic field(pict.2) and an electric field(pict.3), the direction of the ray show that the cathode ray wasa composed of negatively charged fastmovng particles. He called these particles 'electron'.

nucleus
Ernest Rutherford performed he gold foil scattering experiment (pict.4,5)
from the experiment, he concluded that atom is condense in a tiny core(pict.6), and he named it nucleus. The nuclues is small and shoud be with positive charge to balance the charge of electrons

pict4

圖片參考：http://www.hcc.mnscu.edu/chem/V.08/Gold_foil_exp.jpg

pict.5

圖片參考：http://www.hcc.mnscu.edu/chem/V.08/Gold_foil_exp.jpg

pict.6

圖片參考：http://www.hcc.mnscu.edu/chem/V.08/Planetary_model.jpg


neutron

it was found that the atomic msses of atoms are greater that the total masses of prontrons present in the atoms. the existence of neutron was proved by James Chadwick in 1935


2009-07-07 17:33:50 補充：
pict1: http://www.hcc.mnscu.edu/chem/V.08/Gas_Discharge_Tube.jpg
pict2: http://www.hcc.mnscu.edu/chem/V.08/DT_and_Mag_field.jpg
pict3: http://www.hcc.mnscu.edu/chem/V.08/DT_and_electric_field.jpg

2009-07-07 17:33:54 補充：
pict4: http://www.hcc.mnscu.edu/chem/V.08/Gold_foil_exp.jpg
pict5: http://www.hcc.mnscu.edu/chem/V.08/Gold_foil_exp_explanatio.jpg
pict6: http://www.hcc.mnscu.edu/chem/V.08/Planetary_model.jpg

2009-07-08 12:17:25 補充：
pict1: http://www.hcc.mnscu.edu/chem/V.08/Gas_Discharge_Tube.jpg
pict2: http://www.hcc.mnscu.edu/chem/V.08/DT_and_Mag_field.jpg
pict3: http://www.hcc.mnscu.edu/chem/V.08/DT_and_electric_field.jpg

2009-07-08 12:18:38 補充：
pict4: http://www.hcc.mnscu.edu/chem/V.08/Gold_foil_exp.jpg
pict5: http://www.hcc.mnscu.edu/chem/V.08/Gold_foil_exp_explanatio.jpg
pict6: http://www.hcc.mnscu.edu/chem/V.08/Planetary_model.jpg

2009-07-08 12:23:11 補充：
lichunhon6:

neuton 既發現係因為atomic mass 同原子裡既protron既重量不同而知道其存在性

點解知有electron:
用電GE化學反應同放射電子GE放射性物質令佢地知道有D帶負電GE野响原子度, 而靜電同下面proton第一個寫驗令佢地知係响外層同佔左大部份體積

proton:
有個實驗, 用帶正電GE粒子射落D原子度, 睇下會點, 大部分都穿過D原子, 但係有少數向唔同GE角度反彈, 所以就推斷出有點好細GE原子核係帶正電GE

放射性物質都有D係放質子+中子(alpha粒子)

neutron:
一堆正電的粒子堆得咁近會彈開, 所以有neutron隔住

放射性物質都有D係放質子+中子(alpha粒子), 或者齋放中子

2009-07-07 20:16:29 補充：
唔好怪我, 但係我覺得, 無論呢5分邊個攞, 你好似都俾得奀左D

根據我本教科書話"till the end of the 19th centry, scientists still believed that atoms were very tiny 'solid' spheres which cound never be divided. Since then, experiment have shown that atoms are in fact made up of even smaller and simpler particles'

當然科學家是有方法將d sub atomic particles break左佢~~唔係理論