Sorry to get out of order with that last bit on Rutherford. Now back to why Bohr’s model ISN'T the law of the atomic land.

In a simple atom such as hydrogen, where there’s one proton and one electron, quantum mechanics (the physical science used to calculate and analyze the energies and spatial distributions of small particles confined to very small regions of space) calculated hydrogen’s line emission spectrum data (the electron’s absorption or emission of energy whenever it changed energy levels) elegantly. In this simple system, that single electron’s energy emission or absorption was easily quantified, with only a single attractive force acting upon that electron: its one proton.

But let’s take a closer look at the definition of quantum mechanics: small particles, confined to very small regions of space.

We know atoms are minuscule, but to a proton looking out or an electron looking in, the space between them is MASSIVE. Larger atoms have more electrons, and if, according to Bohr’s model, only a defined number of electrons can occupy certain energy level shells (K,L,M,N, etc), electrons will be further and further away from the protons as they also try to put distance between themselves. Thus, larger atoms do not fit the “confined to small spaces” criterion.

Now, imagine the protons and electrons as magnets of opposing charge. When we bring them close together we feel each pulling toward the other. But when we separate them, that pulling force diminishes! Likewise within an atom, we’ve got two basic factors influencing where the electron is in relation to the PROTON: proximity and charge (not taking into account when an electron is ionized, but we’ll get to that later).

If we bring two negative magnets together, we feel one push away from the other, and as we separate them, that repulsive force diminishes. Once again, two factors influencing where an electron is to another ELECTRON: charge and proximity.

An electron’s energy emission or absorption is affected by all these additional forces, for it has to overcome repellent forces from other electrons nearby, as well as attractive forces of an increasing number of protons. It might be easier to see now why Bohr’s model starts to fall apart, right?

Here is the last of the book reviews I'll be covering, as featured from WNYC's Science Friday Broadcast from Sept. 11, 2015: "Buried Sunlight; How fossil fuels have changed the Earth," written by Molly Bang and illustrated by Penny Chisholm.

Whether or not you accept that global warming is taking place, the author Ms Bang frames the changes in the Earth as a result of human presence in a much more basic context. We are being pushed and pulled by media, by politics, and even contradicting evidence from the scientific world, to believe that perhaps it is not human activity that has caused great damage and peril to the planet.  Earth has undergone cycles of warming and cooling throughout its history. Therefore, what does it matter if indeed the Earth is now slowly warming?

The fundamental difference now is that before, those warming and cooling periods took place over hundreds of THOUSANDS of years. Yet the latest measurable changes have occurred in a mere two hundred years. What has been proven in history is that these temperature changes had devastating consequences.

So, given that there is a significant change occurring NOW, and, in a blink of an eye relative to the other temperature fluctuation periods, doesn't it stand to reason that we should make greater efforts to be better stewards for this Earth?

A straightforward, cogent take on our beloved Earth, and the choices we can make to shepherd it into the distant future.

© 2014 The Royal Society of Chemistry

I forgot to mention one more thing about Ernest Rutherford that is truly noteworthy!

Though the periodic table’s "discovery" preceded Rutherford’s discovery of the atomic nucleus by roughly 4 decades, Rutherford’s experiments helped to determine that what was known as the entire positive charge, or atomic number, of the atom, was equal to what was found within a central location of the atom. From this he proposed an inner structure called the nucleus, where the entire positive particulate matter was located within an atom!

In 1870 Dmitri Mendeleev “scooped” Lothar Meyer for publication credit of the periodic table’s hypothesized organization. Not only are elements related physically and chemically depending on atomic number or positive charge, but also, after a certain grouping of elements that increased in atomic number, those similarities would “repeat” in the next grouping of elements. Rutherford, along with fellow scientist H.G. Moseley, performed more experiments that showed that groups of elements with sequential atomic numbers possessed similar nuclear characteristics that could then group them into columns.

Rutherford also discovered that radioactivity was a result of atomic decay. He was quite the prolific experimental scientist, wouldn’t you say? Very deservedly winning the 1908 Nobel Prize for chemistry.

OK, back to our story on how our current atomic model came to be.

Rutherford's atomic model failed to describe electron movement. By laws of physics, electrons should lose energy when in continuous orbit, which then throws the entire atom into an unstable state. But we know the atom is very stable else it couldn’t be a building block.

Bohr built upon Rutherford’s discovery of the nucleus, adding that an electron’s energy dictates the orbital in which it resides. So, electrons with higher energy are able to exist further away from the attractive force of the positively-charged nucleus, while that same attractive force exerted on lower-energy, weaker electrons keeps them closer to the nucleus.

The reason why this was such an important revelation is because it incorporated quantum mechanics to explain, even predict, electron movement. Furthermore, describing orbitals as distinct shells of energy meant knowing the gap from one energy level to the next. So if electrons gained and lost enough energy to hop between levels, those energy absorption and emission packets could be calculated. Data was being collected that described energy emissions, and wouldn’t you know? They matched Bohr’s calculations!

Sadly, orbitals are NOT exactly how electrons move about the atom nor can they accurately describe their location. So, although Bohr’s model took a huge leap forward, it’s still not quite right....

Rutherford was a student of JJ Thomson’s. Known as a creative and collaborative scientist, Rutherford evolved Thomson’s plum pudding model to what is known as the nuclear or planetary model, where most of the atom’s space is actually empty, with some type of positively-charged subatomic particles concentrated in the center. His model differed from Thomson’s model in two key points: 1) there was no positively-charged soup or cloud in which the negatively-charged electrons were embedded, and 2) The positive charge was concentrated centrally, rather than spread uniformly within the atom.
Rutherford had performed experiments leading to his nuclear theory, where he observed that alpha particles that were shot through a gas don’t go straight through. Instead, they got deflected at an angle, therefore there must be something within the atom that repelled them off their linear course.

Rutherford also made important postulations about the nature of elements, which lead to the organization of the periodic chart.

Next up in our trip down history lane of the atomic theory is J.J. Thomson. His model became known as the plum pudding model, named after a British pudding that has, you guessed it, plums embedded in it. This model to me is so intriguing, and here’s why.

Positive charges attract negative charges and vice versa. The way I understand it, is the electrons (which Thomson discovered) were first thought to be these miniscule points of negative charge held by these attractive forces within a positively-charged sphere-shaped cloud. Here’s the thing: electrons move, so Thomson’s thought that as electrons moved further away from the center of the atom, they actually concentrated portions of the positive-charged cloud into concentric spheres, like nesting dolls. The electrons are then more strongly pulled toward the center as they move further away because the sphere of positive charge between it and the center of the atom gets bigger and bigger. Thus the electrons revolve around the center.

Essentially, this gave rise to an orbiting theory for the electrons that are being continually pulled toward the center of the atom, thereby debunking the plum pudding! Unfortunately, this theory too was flawed, and we’ll learn about the succeeding theory which was the pre-cursor to what most of us grew up being taught in school!

Since I so conveniently steered our conversation back to chemistry by talking about atomic models, I thought I’d take a stroll down memory lane on how our current model of the atom developed. This also demonstrates how scientists constantly re-evaluate theory in the face of new evidence. If this is NOT the ultimate example of keeping an open mind, I don’t know what is.

We can go way back the 500’s BC to find theories developing on the concept of atoms. To streamline, let’s start with John Dalton, the first scientist to truly organize elements using the characteristics those of atoms. By experimenting with numerous gases, he observed that the elements that made up the chemical combined in specific ratios. He deduced this by weighing their individual masses. Further employing deductive reasoning, he put together “rules” to describe/predict how elements combine to form chemicals and more specifically, that they combine in specific ratios.

Rather than drawing my own illustration of Dalton’s Atomic model, I felt these original images of Dalton’s would be more impactful to begin our journey. More than a simple list of various elements, Mr. Dalton begins to notice patterns of "behavior" with certain groups of elements, and thus organizes them visually by these characteristics. This will become the prototype for the periodic table.