Bohr Model (Simplified) - Online Tutor, Practice Problems & Exam Prep

In the Bohr model of the atom, electrons occupy circular orbits or shells around the nucleus, with potential energy varying by shell number (n). Electrons can transition between shells through energy absorption or emission, moving to higher energy states (excited state) or returning to lower states (ground state). The energy required for these transitions decreases as shell numbers increase, making it easier for electrons to move between higher shells. Understanding these concepts is crucial for grasping atomic structure and energy dynamics in chemistry.

Bohr Model (Simplified) Concept 1

In the Bohr model of the atom, electrons travel around the nucleus in circular orbits called shells. Now, these shells use the variable n and they're just a grouping of electrons surrounding the nucleus that ties into their potential energy. Potential energy itself is the energy an object possesses, in this case, the electrons based on their given position. So, depending on what shell the electron is found, it will have varying potential energies.

Here, taking a look at Bohr's model of the atom, we have our atom here. Remember, our n variable deals with our shell, or in this case shell number, and also energy level, because again it's attached to potential energy. If we take a look here, we have our nucleus, and in the nucleus, we have our protons and neutrons. After that, we have our first black circular orbit. This represents our first shell. The first shell has an n value equal to 1. In this shell, we have two electrons. Then, the next black circular orbit represents our second shell, so n equals 2. This shell possesses three electrons. So that's the way we observe the atom based on Bohr's model.

Remember, protons are the positively charged particles, neutrons are neutrals, and electrons are the negatively charged ones. The nucleus itself contains our protons and our neutrons. When we're discussing our atom, we have shells containing essentially electrons that move around in an orbit. Based on which shell the electrons are found, their potential energies can vary.

Bohr Model (Simplified) Example 1

What is the value of n for the electron furthest from the nucleus? Alright. So remember, each black circular orbit is a shell. So here, this one is our first shell, so n equals 1. This here is our second shell, so n equals 2. This one here is our third shell, so n equals 3. Remember that we're talking about the electron furthest away from the nucleus. Here is our nucleus. The electron that's furthest away from it is this electron here. It is found in the third shell where n equals 3. So that means that option A would be the correct answer for this example question.

Bohr Model (Simplified) Concept 2

Now within a given atom, we can find electrons within given orbits or shells, but realize through either the absorption or emission of energy electrons are able to move between these different shells. Now, when we talk about absorption and emission, what exactly do we mean? Well, when we say absorption this is when an electron moves from a lower numbered shell to a higher numbered shell, and emission is when the electron does the opposite. It's when an electron moves from a higher numbered shell to a lower numbered shell. If we're to visually see this, here we have absorption in the first image. Here in absorption we're going to say the electron absorbs energy. So basically we have some outside energy source displayed as this energetic photon. That photon is giving its energy to this electron. This electron is initially in the first orbit of the atom, so it's in shell 1. It absorbs this energy and allows it to jump up to a higher energy state, which we call the excited state. So this electron is able to, in this example, go from the first shell to the third shell. Now, if absorption is going up to a higher level, emission is the opposite. Here, realize that that electron can't hold on to that outside energy forever. Eventually, it has to let it go. So here the electron emits, or what we say releases, this excess energy it got from earlier. When it does so, it's going to fall back down to its original position, which we call its ground state. So here the electron goes from the 3rd shell and goes right back down to its initial position which is shell 1.

But how does this relate? How hard is it for electrons to travel between these shells? Well, here we talk about energy transitions. We're saying here as the shell number increases the distance between them is going to decrease. So if you look, this is shell 1, 2, 3, 4, and 5. The distance between shells 1-2 is this big distance here. The distance between shells 2-3 is this distance, the distance between shells 4-5 is this distance, and then you can see that the distance is getting smaller and smaller the higher up we go in terms of shell number. That's because as the distance traveled by an electron increases the then more energy is needed, the energy increases. So basically, what we're saying here is that traveling between shells 1-2 requires the most energy. Look at the distance it has to travel from here all the way up to here. And if we wanted to go from shell 1 to shell 3, that's an even bigger cost. If you're trying to go from shell 1 all the way up to shell 3, look how much bigger the distance is. But then as we're starting up at a higher shell number, less energy is required. So let's say we wanted to go from shell 3 to 5, not as much energy is required. So realize here that distance equals energy. The more electron has to travel then the greater amount of energy is needed. And realize here as the shell number increases then the distance between the shells gets smaller. So it's easier for an electron to go from, let's say, shell 6 to shell 7 than it is from going from shell 1 to shell 2.

Which of the electron transitions represents an example of absorption?

• A. n = 5 to n = 3
• B. n = 1 to n =3
• C. n = 6 to n = 2
• D. n = 7 to n = 4

Which of the electron transitions represents an example of emission?

• A. n = 2 to n = 4
• B. n = 3 to n = 6
• C. n = 3 to n = 1
• D. n = 4 to n = 7

Which of the electron transitions represents an example of absorption with the greatest energy?

• A. n = 1 to n = 4
• B. n = 2 to n =3
• C. n = 6 to n = 7
• D. n = 5 to n = 6

Here’s what students ask on this topic:

What is the Bohr model of the atom?

The Bohr model of the atom describes electrons traveling around the nucleus in circular orbits called shells. Each shell is denoted by a principal quantum number (n) and represents a specific energy level. The nucleus contains protons and neutrons, while electrons occupy these shells. The potential energy of an electron varies depending on its shell. This model helps explain atomic structure and the behavior of electrons in different energy states.

How do electrons transition between shells in the Bohr model?

In the Bohr model, electrons transition between shells through the absorption or emission of energy. Absorption occurs when an electron moves from a lower shell to a higher shell, requiring energy input. Emission happens when an electron releases energy and moves from a higher shell to a lower shell. The energy required for these transitions decreases as the shell number increases, making it easier for electrons to move between higher shells.

What is the significance of the principal quantum number (n) in the Bohr model?

The principal quantum number (n) in the Bohr model represents the shell or energy level of an electron. It determines the electron's potential energy and its distance from the nucleus. Higher values of n correspond to higher energy levels and larger orbits. The principal quantum number is crucial for understanding the arrangement of electrons in an atom and their energy transitions.

What is the difference between the ground state and the excited state of an electron?

The ground state of an electron is its lowest energy state, where it occupies the closest shell to the nucleus. The excited state occurs when an electron absorbs energy and moves to a higher shell, further from the nucleus. The electron cannot remain in the excited state indefinitely and will eventually release the absorbed energy to return to the ground state.

Why does the energy required for electron transitions decrease as shell numbers increase?

As the shell number increases, the distance between successive shells decreases. This means that less energy is required for an electron to move between higher shells compared to lower shells. The energy required for transitions is proportional to the distance the electron must travel, so transitions between higher shells involve smaller energy changes.