What Does an Atom Actually Look Like?

When we think of atoms, many of us picture something akin to our solar system. This is because we often imagine electrons orbiting the nucleus of an atom, similar to how planets revolve around the Sun. However, in reality, atoms do not exist in this way. So, what do they actually look like? 🤔

The quest to understand the structure of the atom began as early as the 18th century. Over the years, several atomic models have been proposed. The starting point for all these models was the solid sphere model of the atom, introduced by "John Dalton" in 1803. According to Dalton, Atoms were considered the smallest unit of matter, incapable of being divided further. The size and type of atoms are not the same across all substances.

Following Dalton, in 1898, the physicist J. J. Thomson proposed a new atomic model. He compared the atom to a watermelon. In his model, the red part of the watermelon represented positively charged matter, while the seeds represented negatively charged particles (electrons). His hypothesis had a significant impact on scientists since he was the one who discovered electrons.

However, Thomson’s model was later disproved by the physicist "Ernest Rutherford", who conducted the gold foil experiment. Rutherford demonstrated that positively charged particles are concentrated in the nucleus at the center of the atom. According to him, electrons revolve around the nucleus, much like planets orbit the Sun. He also discovered that most of an atom consists of empty space. His contributions were crucial in the quest to understand the true structure of the atom.

However, Rutherford could not answer an important question: If the positively charged nucleus attracts negatively charged electrons, why don't the electrons collapse into the nucleus but instead continue to revolve around it?

Bohr's Atomic Model:

Later, in 1913, the "Bohr Atomic Model" proposed by the physicist Niels Bohr brought a new perspective to our understanding of the atom.

According to his model, electrons revolve around the nucleus in specific circular paths, called energy levels. As long as the electrons remain in a particular energy level, they do not emit or absorb energy. Electrons release or absorb specific amounts of energy only when transitioning between energy levels. The electrons revolving in these fixed circular paths maintain a constant angular momentum.

Image created using OpenAI's tools

Electrons revolving in higher energy levels possess more energy, while those in lower energy levels have less energy. The angular velocity of an electron varies depending on the energy level it occupies. However, within each energy level, electrons maintain a uniform angular velocity. Electrons in lower energy levels move at a higher angular velocity, whereas those in higher energy levels move at a lower angular velocity.

This Bohr atomic model was only able to explain the behavior of hydrogen atoms, which have a single electron. It could not account for atoms with multiple electrons and complex energy levels.

Quantum Atomic Model:

Finally, in the 1920s, the Quantum Atomic Model proposed by "Erwin Schrödinger" and "Werner Heisenberg" provided an accurate explanation of the structure of the atom. This quantum atomic model is widely accepted by scientists.

The fundamental idea of this model is that each particle within an atom (such as electrons, protons, and neutrons) behaves not only as a particle but also as a wave. According to this model, electrons do not orbit the nucleus in a particle-like manner. Instead, they exist as clouds spread around the nucleus within specific energy levels.

Image created using OpenAI's tools.

In other words, at every point along an electron's path, there is a probability of finding the electron. Furthermore, according to the quantum atomic model, electrons do not revolve around the nucleus in fixed orbits. Instead, they exist as clouds spread around the nucleus in "descrete energy levels".

These electron clouds have regions of varying density. Areas with higher density indicate a greater probability of finding an electron, while areas with lower density indicate a lesser probability.

Image created using OpenAI's tools

However, the nucleus does not spread out like a cloud. About 99.99% of the total mass of the atom is concentrated in its nucleus. The remaining mass is due to the electrons within the atom.