Welcome back to another post. I hope you all are well.
For some days, I wanted to share something interesting about my studies. Yes, it is about chemistry, which is full of confusion 😅 (just joking). Actually, if we study chemistry with full concentration and try to understand it properly, it becomes easy. And if we have patience, we can enjoy reading it.
Recently, I found something very interesting about the atomic model. In class 9th and 10th, we studied that Thomson’s atomic model and Rutherford’s atomic model were incorrect, and Bohr’s atomic model was correct. At that time, I used to think that science is very confusing. I thought, why do they teach us wrong things first?
But now I understand the reason. Every scientist worked very hard on their experiments. If some experiments failed or were incomplete, we should not make fun of them. Today we only read these experiments, but 100 or more than 100 years ago, scientists actually performed them with great struggle. So studying their work is a way of respecting them.
The first atomic model was Thomson’s atomic model (1904). It is also called the plum pudding, raisin pudding, or watermelon model. According to this model, an atom is a positively charged sphere with electrons embedded uniformly in it. But this model could not explain Rutherford’s alpha scattering experiment and also could not explain the stability of an atom.
Then came Rutherford’s alpha scattering experiment (1908–1911), also known as the gold foil experiment. According to this experiment, most of the space in an atom is empty, and almost all the mass of the atom is concentrated at the centre, called the nucleus, which is positively charged. But this model also had drawbacks. According to Maxwell’s electromagnetic theory, a moving electron should lose energy and fall into the nucleus, so the atom should not be stable. But atoms are stable, so this model was also incorrect.
To overcome these problems and to explain the hydrogen spectrum, Bohr gave his atomic model in 1913, based on Planck’s quantum theory. According to Bohr, electrons revolve around the nucleus in fixed circular orbits. But later, in class 11th, I found that Bohr’s model also failed. It could not explain multielectron atoms, fine and hyperfine spectra, the Zeeman effect, the Stark effect, de Broglie hypothesis, and Heisenberg uncertainty principle.
In 1924, de Broglie proposed that particles like electrons also behave like waves. In 1927, Davisson and Germer proved this through an experiment. Then came the Heisenberg uncertainty principle, which says that we cannot know both the exact position and exact velocity of an electron at the same time.
So the main reason Bohr’s model failed is that Bohr treated the electron only as a particle moving in a fixed orbit, but de Broglie showed that electrons have wave nature, and Heisenberg proved that exact position and velocity cannot be known together.
Because classical mechanics failed to explain the behaviour of microscopic particles, a new branch of science called quantum mechanics was developed. After this, the quantum mechanical model of the atom, Schrödinger wave equation, and different quantum numbers were introduced.
So this is the short story of atomic models. It is tricky, but very interesting. If someone has patience, they can really enjoy this topic. And if anyone has doubts, they can search more about it.
Also, tell me in the comments, who is a chemistry lover?
