Category: Quantizing the Atom

The success of Bohr’s atom depended on the notion that certain orbits were special, and when electrons occupied these they refrained from radiating away. Physicists were eventually persuaded to buy this, but only because it allowed them to predict the frequency of atomic spectral lines and many other observed atomic phenomenon. Stationary states could not…

Bohr could have easily stopped there, satisfied with inventing a (semi) quantum model for the one-electron hydrogen. But he didn’t. His was an inquiring mind, and it wanted to know what insights could be gleaned by applying his postulate to atoms with 2, 3, or even 92 electrons. He approached this problem by extending his…

The Bohr atom gave physicists a wonderful basis upon which to visualize and interpret the inner workings of the hydrogen atom. To explore this further, we would benefit from a system to keep track of all the stationary states and energy levels we’ll encounter. To do so, Bohr introduced a counting system based on what…

Having established the “house rules” governing the hydrogen atom’s behavior, Bohr set to work calculating what these would imply in terms of observable phenomenon. He did so by applying nothing more than Newton’s laws, Maxwell’s equations, and the conservation of energy. Throwing in a sprinkle of algebra for good measure, he first made an estimate…

Just as Planck and Einstein had done before, Bohr’s “solution” began with a set of bold postulates. In his case, four of them. Like his predecessors, he could not really explain their underlying basis. But when he took these as his starting point, and then applied the well-established principles of classical physics, he arrived at…

Almost immediately after Bohr arrived in Manchester, he made a very important discovery: he wasn’t quite cut out for laboratory work. It was much better for him (and the future of physics) to be seated at a desk and tasked with deriving new formulas. Rutherford agreed, and before long Bohr began a fateful quest to…

Although the most catastrophic, the atomic spiral wasn’t the only mystery of the Rutherford atom. Unlike the continuous spectra emitted by heated solids, you’ll recall that excited gases emit and absorb light in the form of distinct spectral lines. The spacing of these is unique to the particular type of gas being observed. In the…

We explained away doubts about the stability of Rutherford’s nuclear atom by stating, simply, that the electron must orbit the nucleus like the moon about Earth. We confess now to telling you only half the story. By setting the electron in motion about the nucleus, we actually doomed it to an even grimmer fate. The…

We return now to England to see if there have been any new developments in the theory of the atom. Ernest Rutherford had just unveiled a new model for the atom—the nuclear atom—that seemed to be in better agreement with experimental observation than the plum pudding model of J. J. Thomson. Since then, little new…

We will revisit the atom, and learn how the decisive blow in the battle between Thomson’s plum pudding model and Rutherford’s nuclear model was dealt by a student of them both. We will learn about yet another success of quantum ideas, this time to explain the inner (and outer) workings of the atom. We’ll discover…