玻尔的原子模型
尼尔·玻尔提出了玻尔模型,是基于对卢瑟福原子模型的修改。卢瑟福的模型引入了原子核模型,其中解释了带正电的原子核被称为电子的带负电粒子包围。玻尔修改了它,解释说电子在固定轨道中移动,而不是在两者之间。他接着说,每个贝壳都有一个特定的能级。结果,卢瑟福解释了原子核,玻尔把它变成了电子及其能级。
卢瑟福的原子模型
在他的实验中,卢瑟福将来自放射源的高能 α 粒子流瞄准了一片金薄层(100 纳米厚)。为了分析 α 粒子产生的偏转,他在薄金箔周围覆盖了一个荧光硫化锌屏幕。卢瑟福的观察在某些方面与汤姆逊的原子模型相矛盾。
卢瑟福的 Alpha 散射实验的观察结果:
- 因为射向金片的大部分 α 粒子通过它而没有被偏转,所以一个原子中的大部分空间是空的。
- 金片以较小的角度偏转一些α粒子,导致每个原子中的正电荷分布不均匀。原子中的正电荷集中在原子的一小部分区域。
- 只有少数阿尔法粒子被偏转回来,这意味着只有少数阿尔法粒子具有接近 180 度的偏转角。结果,与原子的总体积相比,原子中带正电的粒子占据的体积非常小。
卢瑟福模型的局限性:
- 根据卢瑟福的说法,电子在称为轨道的设定轨迹中围绕原子核运行。根据麦克斯韦的说法,加速的带电粒子会发射电磁辐射,因此围绕原子核旋转的电子也应该这样做。这种辐射会传输来自电子运动的能量,但会以轨道收缩为代价。电子最终会在原子核中坍缩。根据计算,使用卢瑟福模型,一个电子将在不到 10-8 秒的时间内在原子核中解体。结果,卢瑟福模型与麦克斯韦理论相矛盾,无法解释原子稳定性。
- 卢瑟福模型中的一个问题是他忽略了原子中的电子排列,使他的理论不完整。
- 尽管早期的原子模型是错误的并且无法解释某些实验结果,但它们为未来的量子力学突破奠定了基础。
玻尔原子模型
Bohr’s model consists of a small nucleus (positively charged) surrounded by negative electrons moving around the nucleus in orbits where he found out that an electron located away from the nucleus has more energy as compared to electrons close to the nucleus.
玻尔的原子模型可以描述为一个原子由三个亚原子粒子组成——质子、电子、中子。质子是一种带正电的粒子,是所有原子核的基本成分。它是最轻和最稳定的,并且具有与电子大小相等的电荷。电子是一种粒子,它是物质的基本组成部分,独立存在或作为原子核外的组成部分存在。中子是一种基本粒子,不带电荷,其质量略大于质子。质子和中子位于原子核心的一个微小原子核中。
The electrons spin rapidly around the nucleus in circular routes known as energy levels or shells. The number of electrons that each shell can hold is limited. The formula is, 2n2 where n is the orbit number or energy level index.
每个能级都与固定量的能量相关联,只要电子在同一能级上继续旋转,电子的能量就不会发生变化,并且原子保持稳定。
玻尔原子模型的公设
- 在原子中,带负电的电子围绕带正电的原子核以称为轨道或壳的圆形路径旋转。
- 每个轨道或壳具有固定的能量,称为轨道壳。
- 能级用整数表示(n=1、2、3…)。这些整数也称为量子数,从n=1的原子核开始,具有最低的能级。当一个电子达到最低能级时,就说它处于基态。
- 当电子获得能量时,它们会从较低能级移动到较高能级。当它们失去能量时,它们会从较高的能量水平移动到较低的能量水平。
玻尔原子模型的局限性
- 它未能解释塞曼效应。在存在静磁场的情况下,塞曼效应会导致谱线分裂成许多分量。这类似于斯塔克效应。
- 它也未能解释斯塔克效应。斯塔克效应是在存在电场的情况下将谱线分成几个分量。
- 它违反了海森堡不确定性原理,无法解释更大原子的光谱。这个概念断言,一个物体的位置和速度不能同时精确地确定。事实上,在自然界中,绝对位置和精确速度的概念是没有关系的。
示例问题
问题一:玻尔模型和卢瑟福模型有什么关系?
解决方案:
Bohr’s model was formed by the modification of Rutherford’s model of an atom that introduced nuclear model of an atom wherein it was explained that nucleus which is positively charged is surrounded by negatively charged electrons. It was modified by Bohr where he explained that electrons move in fixed orbitals and not anywhere in between. It was also explained that each shell has a fixed energy level.
问题2:玻尔的原子模型是什么?
解决方案:
Bohr’s model consists of a small nucleus (positively charged) surrounded by negative electrons moving around the nucleus in orbits where he found out that an electron located away from the nucleus has more energy as compared to electrons close to the nucleus.
问题 3:电子在玻尔模型中如何运动?
解决方案:
Electrons in atoms travel around a central nucleus in circular orbits and can only orbit stably at a fixed set of distances from the nucleus in circular orbits that are related to energies.
问题 4:索末菲如何修正玻尔的理论?
解决方案:
Sommerfeld model suggested that electrons move around a nucleus in elliptical orbits instead of circular orbits. The Bohr – Sommerfeld model was incoherent that contributed to many paradoxes.
问题 5:卢瑟福原子模型的局限性是什么?
解决方案:
According to Rutherford, electrons orbit the nucleus in set trajectories termed orbits. According to Maxwell, accelerated charged particles emit electromagnetic radiation, so an electron revolving around the nucleus should do the same. This radiation would transmit energy from the electron’s motion, but at the expense of orbital shrinkage. The electrons would eventually collapse in the nucleus. According to calculations, an electron would disintegrate in the nucleus in less than 10-8 seconds using the Rutherford model. As a result, the Rutherford model contradicted Maxwell’s theory and was unable to explain atom stability.
One of the problems in Rutherford’s model was that he ignored the electron arrangement in an atom, leaving his theory incomplete.
Despite the fact that the early atomic models were erroneous and failed to explain certain experimental results, they served as the foundation for future quantum mechanics breakthroughs.