Carbon has the atomic number 6 and is denoted by the symbol C. It forms around 0.025% of the earth’s crust, making it the 15th most abundant element. It is the most common element found in all known life forms owing to its ability to form polymers at the temperatures normally prevalent on the earth’s surface.
Carbon atoms are capable of bonding with each other in different ways resulting in the formation of allotropes of carbon. It exists in four allotropic forms: diamond, graphite, fullerenes, and amorphous carbon.
In this article, we will discuss carbon and its Bohr model.
So, let’s begin.
Bohr Model of Carbon
After several failed attempts to explain the structure of the atom, Ernst Rutherford proposed his hypothesis in 1911.
He explained that the atom is divided into a stationary positively charged nucleus and the negatively charged electrons that revolve around this nucleus, just like the planets around the sun in our solar system. That is why this model was also known as the planetary model of atomic structure.
Also, the nucleus of the atom was made up of two atomic species, viz. neutral neutrons, and positive protons.
Although this model explained most of the properties of an atom, it was accompanied by certain drawbacks. The major argument against this model was about the stability of the atom.
The question was that if the electrons were continuously in motion, they would slowly gain some acceleration and, thus, energy. As this energy increases, it becomes impossible for the electrons to keep moving inside the radius of the atom. This makes the atom unstable
Rutherford was unable to answer these queries, due to which this model was also about to get discarded. However, in 1916, Niel Bohr came out with the solution.
Bohr explained that the electrons do not move around the nucleus in random directions; rather, they follow fixed orbits, also known as shells.
He further stated that these shells have specific energies associated with them, which is why they are also known as energy levels.
He named these shells K, L, M, N, etc., in alphabetical order and 1, 2, 3, 4, etc., in the numerical order increasing from inside to outside. He stated that the energies of these shells also increase from inside to outside.
Therefore, the electrons housed in the shells located closest to the nucleus had minimum energy, while the electrons located in the outermost shell have maximum energy.
The electrons can also move from one orbit to another based on their energies. As an electron absorbs energy, it moves from lower to higher energy levels. Similarly, if an electron loses energy, it moves from higher to lower energy levels.
The electrons located in the outermost energy level participate in bond formation between different as well as similar atoms. These are known as valence electrons, and the shell is known as the valence shell.
These postulates given by Bohr, along with those given by Rutherford, came to be known as the Bohr˗Rutherford model, or simply, the Bohr model of the atom.
In the case of the Carbon atom, there are 6 protons, 6 neutrons, and 6 electrons. The electrons are distributed in two shells, viz. K and L shell.
|No. of Proton||6|
|No. of Neutron||6|
|Number of Electron||6|
|Number of shells||2|
|Number of electrons in first (K) shell||2|
|Number of electrons in second (L) shell||4|
|Number of valence electrons||4|
Drawing the Bohr Model of Carbon
Carbon is a member of group 14 and period 2 of the Periodic table.
The information that we can infer from the above-mentioned Carbon box is as follows:
• The atomic number of Carbon is 6.
• The electronic configuration of Carbon is [He] 2s22p2.
• The atomic symbol of Carbon is C.
• The atomic mass of Carbon is 12.0096.
We will use this information to draw the Bohr model of the carbon atom.
In the first step, we will draw the nucleus of the carbon atom. For this, we will first have to calculate the number of protons and neutrons present in this atom.
The atomic number symbolizes the number of protons in an atom.
In the case of the carbon atom, atomic number = 6
Therefore, the number of protons in the carbon atom = 6
Now, we will calculate the number of neutrons in the carbon atom.
For an atom, the number of neutrons is calculated using the formula:
Using this formula, we will calculate the number of neutrons in the carbon atom.
The atomic mass of carbon is 12.0096. Rounding it up to the nearest whole number, we get 12.
Now, we will put this in the formula mentioned above.
Hence, the number of neutrons in the carbon atom =12 ˗ 6 = 6
Now that we know the number of protons and neutrons in the carbon atom, we will draw the nucleus of this atom which appears as follows:
Now, we will move forward to draw the shells of the carbon atom. For this, we would require calculating the number of electrons in this atom.
Just like protons, the number of electrons is also equal to the atom’s atomic number.
Therefore, the number of electrons in the carbon atom = 6
Now we will fill these electrons in different shells of the carbon atom.
Before we begin, we must understand the rules that are followed while filling the electrons in the shells.
The electrons in any shell are always filled in the clockwise direction, in a group of four, except when less than 4 electrons are remaining to be filled.
The clockwise format means that the first electron in a shell is placed at the 12 o’clock position, the second at the 3 o’clock position, the third at the 6 o’clock position, and the fourth at the 9 o’clock position, respectively. After this, the next batch of four electrons is added to the shell in the same pattern.
However, the K shell of an atom is an exception to this rule, where the electrons are placed at the 12 o’clock position only.
The maximum number of electrons that can be filled in a shell is given by the formula 2n2.
Now, we will fill the electrons inside different shells of the carbon atom.
We will begin with the innermost shell i.e., the K shell.
Calculating the number of electrons that can be filled in the K shell of the carbon atom using the above-mentioned formula, we get 2 (1)2 = 2.
Therefore, the maximum number of electrons that can be housed in the K shell of the carbon atom is 2.
After filling these 2 electrons in the K shell, the carbon atom appears as follows:
Now, when the K shell of the atom is complete, we will move forward to fill the next shell, i.e., the L shell of the carbon atom.
Calculating the maximum number of electrons that can be accommodated in the L shell of the carbon atom, we get 2 (2)2 = 8.
Hence, the maximum number of electrons housed in the carbon atom’s L shell is 8.
However, looking at the total number of electrons present in the carbon atom, i.e., 6, as we have already filled 2 electrons in the K shell, we are only left with four electrons.
Therefore, the number of electrons present in the carbon atom’s L shell is 4.
Now, we will fill these electrons in the L shell of the carbon atom in a clockwise manner.
After filling the L shell, the Bohr model of the carbon atom is complete. Therefore, the final Bohr model of carbon appears as follows:
Hence, the final Bohr model of the Carbon atom consists of 6 protons, 6 neutrons, and 6 electrons.
The 6 protons and 6 neutrons are housed in the carbon atom’s nucleus while the 6 electrons are filled in the two shells, i.e., K and L shells, as 2 and 4, respectively.
Deriving Lewis Structure of Carbon atom from Bohr model
The Lewis structure of an atom, also known as the Lewis dot structure or electron dot structure, is a pictorial representation that depicts the nucleus of the atom, represented with the atomic symbol of the particular atom and the valence electrons of the atom.
This model was introduced by Gilbert N. Lewis in 1916 and is used to represent the covalent bonding between atoms. However, this structure can also be drawn for individual atoms.
As the electrons are shown as dots in the structure, the name electron dot is given to this model.
The Lewis structure of the carbon atom appears as follows:
• How many shells are present in the Bohr model of carbon?
The carbon atoms consist of 6 electrons that are distributed in 2 shells, i.e., K and L shells.
• How many electrons are housed in the valence shell of the carbon atom?
The valence shell, i.e., the L shell of the carbon atom, consists of 4 electrons.
• What is the number of protons and neutrons present in the carbon atom?
The carbon atom consists of 6 protons and 6 neutrons inside the nucleus.
• The final Bohr model of the Carbon atom consists of 6 protons, 6 neutrons, and 6 electrons, respectively.
• The protons and neutrons are placed inside the nucleus, which is a positively charged entity located at the center of the atom
• The electrons are housed in two shells, i.e., K and L shells as 2 and 4, respectively.