接着 Marie Curie从一吨沥青铀矿中分离出约0.2g的一种新元素化合物(溴 化物),这种新元素被命名为镭( radium)。美国化学家卢瑟福进一步研究了放 射性的本质: revealed three types of radiation: alpha(a),beta(B), and gamma(y) Type of radiation Charge Nature Alpha 4.0026 Nuclear of helium atom l/1837 High-speed electron Gamma High-energy radiation (2)Rutherfords experiment on the scattering of a particles a. J.J. Thomson proposed that the atom consisted of a uniform positive sphere of matter in which the electrons were embedded This model became known as the plum-pudding " model, after the name of a traditional English dessert. Thomson atomic model was very short-lived b. In 1910 Rutherford and his co-workers performed an experiment( 7.3 )that led to the downfall of thomson' s model on the scattering of a particles.他们让a粒子通过 1000层金原子(400m)的金箔,发现大偏转的a粒子出现的几率为1/103,即 10万个a粒子中,只有一个a粒子发生90°以上的偏转。 他得出了如下的结论:()原子中大部分空间是空的;(i)原子核的正电荷和 质量都集中在一个很小体积的小球上。通过一层原子时,大偏折a粒子的几率 为10-8,这说明S/S=10-8,∴,r/簟子=10-4。根据这些结果,卢瑟福 提出了原子有核模型。 Figure 7.3(a)A block-diagram of the Rutherford-Marsden-Geiger experiment Most of the a-particles pass through the empty space between nuclei. A few come close nough to be repelled by the nucleus, and these particles are deflected through small angles. Occasionally, an a-particle travels along a path that would lead to a direct hit with the nucleus. These particles are deflected through large angles by the force of repul sion between the a-particle and the positively charged nucleus of the atom 4.质子的发现( Discovery of proton) 886年 Goldstein把阴极制成多孔的阴极,发现有另外一种射线从阴极向与电子 发射方向的相反的方向射出,它由残留在真空管的气体的正离子组成,称为阳极射 线。若残留气体是氢气,那么组成阳极射线的将是氢离子(H),即氢原子核,起 名为质子。 5.中子的发现( Discovery of neutron) 1932年 Chadwick( British scientist)(1891-1972)发现,当用α粒子辐照金属铍 时,产生一种有强穿透性的射线,是由中子组成的98 接着 Marie Curie 从一吨沥青铀矿中分离出约 0.2g 的一种新元素化合物（溴 化物），这种新元素被命名为镭（radium）。美国化学家卢瑟福进一步研究了放 射性的本质：revealed three types of radiation：alpha (α), beta (β), and gamma (γ) ： Type of radiation Mass Charge Nature Alpha 4.0026 +2 Nuclear of helium atom Beta 1/1837 −1 High-speed electron Gamma 0 0 High-energy radiation (2) Rutherford’s experiment on the scattering of α particles a．J. J. Thomson proposed that the atom consisted of a uniform positive sphere of matter in which the electrons were embedded. This model became known as the “plum-pudding” model, after the name of a traditional English dessert. Thomson’s atomic model was very short-lived. b．In 1910 Rutherford and his co-workers performed an experiment ( 图 7.3 ) that led to the downfall of Thomson’s model on the scattering of α particles. 他们让 α 粒子通过 1000 层金原子(400 nm )的金箔，发现大偏转的 α 粒子出现的几率为 5 1/10 ，即 10 万个 α 粒子中，只有一个 α 粒子发生 90°以上的偏转。 他得出了如下的结论：(i) 原子中大部分空间是空的；(ii) 原子核的正电荷和 质量都集中在一个很小体积的小球上。通过一层原子时，大偏折 α 粒子的几率 为 10−8，这说明 S 原子核 / S 原子= 10−8，∴r 原子核 /r 原子= 10−4。根据这些结果，卢瑟福 提出了原子有核模型。 4．质子的发现（Discovery of proton） 1886 年 Goldstein 把阴极制成多孔的阴极，发现有另外一种射线从阴极向与电子 发射方向的相反的方向射出，它由残留在真空管的气体的正离子组成，称为阳极射 线。若残留气体是氢气，那么组成阳极射线的将是氢离子（H ＋），即氢原子核，起 名为质子。 5．中子的发现（Discovery of neutron） 1932 年 Chadwick (British scientist)（1891-1972）发现，当用 α 粒子辐照金属铍 时，产生一种有强穿透性的射线，是由中子组成的