What rule/principle states that electrons fill orbitals from l...

Question

What rule/principle states that electrons fill orbitals from lowest energy to highest energy?

Accepted Answer

Welcome back, everyone. Which of the following principles states that a maximum of two electrons with opposite spins can occupy a single atomic orbital. We have choice. A, the poly exclusion principle. Choice B alba principle C Hunt's rule or law of conservation of mass. Let's start by breaking down each enter choice and starting with the poly exclusion principle, I'm going to represent an orbital within an atom as a circle. And I'm going to, we need to recall that according to the poly exclusion principle, if we say this orbital has two electrons, the electrons should be filled in the single orbital with opposite spins. So we would represent the first electron as an upward half arrow and the second electron, we would pair it up with the first as a downward half arrow. So we can say opposite spins is going to be a must for paired electrons in an orbital. So based on our prompt choice, a looks like a good option. But let's move on to choice. B, the abou principle, we're going to draw an energy level orbital diagram. And let's start with the one s sublevel which begins with just one orbital because it's the S sublevel which can hold a maximum of two electrons. And then say we fill in the two S orbital or sorry, the two S sublevel with its one S orbital moving on up in energy, we then have the two P orbital which contains a total, the two P sublevel which contains a total of three orbitals. Beyond that in energy, we hit the three S sublevel containing just one orbital represented as a line. And followed by that, we have the three P sublevel rather orbital because it's within the P orbital. And at the third energy level, recall that the P orbital, as we stated before has three orbitals total holding a maximum of six electrons. Beyond that in energy, we then have the four S subs shell represented by its single orbital. And followed by that in higher energy, we have the 3d sublevel which consists of a total of five orbitals. And then lastly, we'll stop at the four P containing its three orbitals. Let's say we are filling in this energy diagram for an atom like barium. And so recall that Beli has an atomic number or Z value equal to four, signifying four electrons total that we can fill in. So recall that according to the alpha principle, we start from the lowest energy level which would be the one S sublevel for beri. And because it only has four electrons, and we understand that the S sublevel should only hold a maximum of two electrons in its single orbital. If brillion has four electrons total, we would fill in the first two electrons as opposite half spins paired in the first sublevel. And then we would take care of the last two electrons at the highest energy level for Brim, which is going to be the two s sublevel. So that is then where we fill in the remaining two electrons as paired opposite spins. So because our does not have anything to do with energy levels. As far as principles when completing orbital diagrams for an atom, we would rule out choice b the alpha principle. But let's move on to choice C and consider Hun's rule. Let's think of filling in the two P sublevel for carbon where carbon recall has an atomic number or Z value equal to six signifying six electrons. And as we stated before, the two P orbital consists of a total of three orbitals recall the electron configuration of carbon, which is one s two, I'm sorry, the two should be in the exponent. So one s 22 S 22 P two, we would count to two units in the P sublevel to hit carbon. So if we're filling in the two P orbitals for carbon, it only has two electrons given by that Exxon of two in its electron configuration. So two electrons that we must fill in. And according to Hun's rule, we would fill in the electrons in a single orbital singly before doubly. So we would fill in the first electron of the two p orbital for carbon as any direction arrow you'd like I chose an upward arrow for one electron. And then we move on to the second orbital in the two p sublevel of carbon. And we would fill in the second electron completing the filled two p orbital for carbon, which we would have as singly drawn in electrons in the first two orbitals of the three making up the two p sublevel for carbon. And that is how we explain Hans rule. Now, although we did use and actually the electron should be the same spin when singly filling them up. So we started with an upward spin in my drawing. But because the prompt is specifically with regard to a maximum of two electrons occupying a single electron orbital, as we stated, the best principle for that is the poly exclusion principle where when you're pairing electrons, they should be with opposite spin. Whereas in Hunt's rule, it's really just more focused on single filling in orbitals before pairing any electrons for a given configuration of an atom. So for that reason, let's rule out choice c because choice a still looks like the best choice so far. And lastly, that leaves us with the law of conservation of mass. So for this law, let's imagine a chemical reaction. So let's imagine hydrogen gas combining with oxygen gas to form water as a product. So hydrogen and oxygen would make up the reactants and water is the product. So according to the law of conservation of mass, the sum of the masses of the reactants is going to be equal to the sum of the masses of the products. So ultimately, what that tells us is that total mass for a given reaction remains the same before and after a chemical reaction. And our prompt has nothing to do with mass. So we would rule out choice D for that reason. And that allows us to confirm that choice. A, the poly exclusion principle is the principle stating that a maximum of two electrons with opposite spins can occupy a single atomic orbital. I hope that this made sense and let us know if you have any questions.

Struggling with General Chemistry?

What rule/principle states that electrons fill orbitals from lowest energy to highest energy?

Watch next

Quantum Numbers: Spin Quantum Number practice set