Question

Running into a bit of confusion trying to understand the atomic structure and the root cause is mostly related to orbitals and energy levels.

At a basic level, I was taught that electrons orbit the nucleus in fixed, circular orbits called "electron shells." New information that I’ve learned states that there is some uncertainty in the positions of electrons at a given time. For example, although the one electron in a Hydrogen atom orbits the nucleus at the first energy level, its position is uncertain, that is, it can be further away from the nucleus or much closer.

To show where electrons are most likely to be found, orbitals are used which depict a region in which an electron will be 90% of the time.

The problem in my understanding lies with energy levels. The first energy level has an orbital called 1s and has a spherical shape with the nucleus at its center. How could an electron be classified as being in the first energy level when it’s possible that it can be found right near the nucleus? Similarly, the second energy level contains a spherical orbital as well called 2s. How could we say an electron is at the second energy level when it can very well be found much lower than that energy level according to the 2s orbital? It’s hard to see how orbitals and energy levels exist at once: one says an electron can be found near the nucleus whilst the other says it must be orbiting in the second energy level.

I’d greatly appreciate it if the explanation is sufficient enough for an As level student.

Answer 1

Electrons exist in discrete energy levels within an atom, with a quantized amount of energy corresponding to each level. Orbitals describe areas where electrons are most likely to be found, and while there's uncertainty in an electron's exact position, it will still belong to a particular energy level based on its energy.

Step-by-step explanation:

Understanding the structure of an atom involves comprehending both energy levels and orbitals. The confusion often arises when trying to picture how an electron can simultaneously exist in a discrete energy level while also having an uncertain position within an orbital. Let's clarify this.

Energy levels, also known as electron shells, are like the steps of a staircase around the nucleus of an atom. The first energy level is closest to the nucleus and holds electrons with the lowest energy.

As electrons move to higher energy levels, their energy increases. The maximum number of electrons in a particular energy level is determined by the number of orbitals, with up to two electrons per orbital.

Orbitals, on the other hand, describe the probability of finding an electron in a certain region of space. They are not fixed tracks like the orbits in the Bohr model, but rather regions where an electron is likely to be located 90% of the time.

The 1s orbital at the first energy level, for example, is spherical and describes a region where the electron is most likely to be found, although its exact position at any given moment is uncertain.

Even when an electron is in the 2s orbital of the second energy level, it can sometimes be found closer to the nucleus within the orbital space. However, it still belongs to the second energy level due to its energy which is higher than that of electrons in the first energy level.

Electron energy is quantized, meaning an electron cannot have just any energy but must have specific energy levels. Even if an electron in a 2s orbital comes close to the nucleus, it won't have the same energy as electrons in the 1s orbital, hence we say it's in the second energy level.

The positively charged protons in the nucleus stabilize the electronic orbitals through electrostatic attraction, maintaining the integrity of the energy levels while accommodating the probabilistic nature of the orbitals.