Current Atomic Model

For years and years atomic models have been changing as physics evolved. Everyone could explain certain properties of atoms. However, there were experimental results that did not agree with the theory, uncovering its inadequacies.

And then… What is the current atomic model?

Well, it turns out that in the 20s of the last century one of the most beautiful and most inexplicable theories emerged that we have today: quantum mechanics.

This strange but amazing theory allows us to model phenomena in the microscopic world in a very precise way.

EXACT!

With it we can study atoms with precision and mathematically explain what we see in experiments.

Before starting it is important that you know what an atom is. I invite you to read our extensive article on the atom.

The current quantum atomic model, known as the quantum atomic model, represents the most advanced and precise understanding of the structure and behavior of the atom, based on the principles of quantum mechanics. This model transcends classical notions, replacing the defined orbits of electrons with probability regions where they are most likely to be found.

By integrating concepts such as wave-particle duality and the uncertainty principle, The quantum model offers a detailed description that allows us to explain and predict a wide range of physical and chemical phenomena. with unprecedented precision. In essence, this model is not only fundamental to modern physics and chemistry, but is also crucial to advanced technologies ranging from electronics to medicine.

Let's go in parts.

To study atoms through quantum mechanics we have two options: use Schrödinger's integral-differential equations or Heisenberg's matrix equations. These two approaches are equivalent.

In this case we will use the Schrodinger equation to try to explain the modern atomic model.

In this theoretical framework, we have the nucleus of the atom in the center and then electrons “around it.” Unlike other older models, electrons no longer follow orbits, but are found in orbitals. This is because electrons are modeled using a wave function and are no longer treated as if they were point particles.

And what does this mean?

This means that the electrons no longer have a fixed position, but can be in several places at the same time. This is known as quantum superposition.

Therefore, instead of having positions, we have a probabilistic distribution of which are the areas around the nucleus with a greater probability of finding electrons.

The current model of the atom is based on the principles of quantum mechanics, representing a significant evolution from the simpler models proposed in the past. This model does not describe electrons as particles in fixed orbits around the nucleus, but as probability waves distributed in regions of space called atomic orbitals. Here are the key features of the quantum model of the atom:

PERFECT!

We now have a basic idea of ​​the modern atomic model. And now that?

Now it's time to understand the characteristics of the electrons in this model and how we use the Schrödinger equation to understand them.

The equation proposed by Erwin Schrödinger is very complicated to solve mathematically. That is why it can only be solved for hydrogenoid atoms, which only have one proton and one electron. With atoms that have a higher number of electrons we can only obtain approximate solutions.

When we develop this equation we see that there are certain values ​​that are parameterized and can only take certain values. These values ​​are called quantum numbers and allow us to describe the properties of the different electrons in the nucleus of an electron.

I DON'T UNDERSTAND ANYTHING!

If this is the first time you are reading this about quantum numbers, you probably have not understood the concept. We could say that there are different types of electrons depending on where they are in the nucleus. These electrons have different energies and have different “shapes.” In order to describe each electron we use quantum numbers that tell us the energy and shape that each electron has.

Better with this explanation?

In addition, there is a fourth quantum number that does not come out of the Schrödinger equation: the spin quantum number.

If you are new to this world, you are probably wondering: But what the hell is spin?

But do not worry!

For this explanation, with a simple simile you will conceptually understand what spin is.

Electrons have the property of “spinning” on themselves. If they turn to the right we will say that they have spin-up and if they turn to the left we will say that they have spin-down. Thus, the magnetic quantum number simply indicates the direction of spin of the electron. If it is spin-up, the associated magnetic quantum number is +1/2. On the other hand, if it is spin-down, the associated number is -1/2.

The most recent atomic model, the one we have today, is actually not entirely Schrödinger's model. This is because there are inadequacies in it and therefore we have had to adopt certain corrections to improve them.

As we have seen, spin quantum numbers do not arise naturally from the Schrödinger equations. Therefore, they had to be added a posteriori, giving rise to the Schrödinger-Pauli atomic model.

In certain types of very heavy atoms, the forces between electrons within the nucleus mean that the electrons can reach very high speeds. At this point, relativistic effects become important. Therefore, we have to add corrections to be able to take into account the effects of Einstein's special relativity.

These corrections are carried out through the Dirac equation. Paul Dirac managed to unify the formula that describes energy in relativity (E=mc2) and the Schrödinger equation. Adding this correction needed.

The evolution of the atomic model reflects how our understanding of matter has advanced from primitive philosophical ideas to sophisticated quantum theories. Over the centuries, the notion of the atom has been refined through the contributions of many prominent scientists, each contributing a crucial piece to the complex puzzle of what we know today about atomic structure.

The Greek philosopher Democritus was one of the first to suggest the idea that matter was composed of indivisible, invisible particles that he called atoms. Although his theory was purely speculative and lacked experimental basis, he laid the foundation for future research on the composition of matter.

In the 19th century, John Dalton revitalized the idea of ​​the atom with his atomic theory, proposing that each chemical element was composed of atoms of a unique type. Dalton introduced concepts such as atomic weight and established the foundation for understanding chemical reactions in terms of the joining and separation of atoms.

J.J. Thomson discovered the electron in the late 19th century, which led to the development of the atomic model of it, known as the "plum pudding". He proposed that atoms were positively charged spheres with embedded electrons, a theory that explained the existence of negatively charged subatomic particles within the atom.

Thomson's model was replaced by the nuclear model of Ernest Rutherford, who, based on his alpha particle scattering experiments, concluded that the atom had a dense, positively charged nucleus in the center, with electrons orbiting around it.

Niels Bohr developed an atomic model that incorporated energy quantization to explain the stable orbits of electrons and the emission spectra of atoms. His model introduced fixed circular orbits in which electrons could move without radiating energy.

Bohr's model evolved with the development of quantum mechanics in the first half of the 20th century. Scientists such as Schrödinger, Heisenberg and Pauli contributed to a more sophisticated model where electron positions are described by probabilities rather than defined orbits, giving rise to the modern atomic model.