Phosphorous is denoted by the symbol P and has the atomic number 15. Phosphorous is highly reactive and occurs in abundance in the earth’s crust, in the form of minerals. Majorly, two forms of phosphorous are known to occur viz. white phosphorous and red phosphorous.
White phosphorous is also known to exhibit chemiluminescence i.e. it glows faintly upon exposure to oxygen. Phosphorous, in the form of phosphate ions i.e. PO4–, is an important nutrient element required for various vital activities of many living beings.
Hello people!!! In this article, we will answer all your queries related to the Bohr model of phosphorous, and some more.
So just keep reading to get your facts clear…
Bohr Model of Phosphorous
Bohr’s atomic model is actually the modification of the Rutherford model of the atom. The Rutherford model was presented in 1911 and it correctly depicted the position as well as the charge of various atomic species.
However, there were a few drawbacks to this model. This model could stand right in terms of certain concepts of classical mechanics and electromagnetic theory.
Niel Bohr, in 1913, presented the Rutherford model with the required corrections, and this model since forth has been recognized as the Bohr-Rutherford model of the atom.
The Bohr model presents a pictorial illustration of the structure of an atom with specific locations of different atomic particles. The charge, as well as the number of particles, is also specified in the model.
To understand this model better, we first need to understand the terminology used in this model for explaining the atomic structure. A few important terms are:
• Nucleus: This is the center or core of the atom. The nucleus can be compared with the sun in the solar system. It is made of two types of atomic particles viz. protons and neutrons.
• Protons: These are the positively charged particles located inside the nucleus of an atom. They are responsible for the positive charge carried by the nucleus.
• Neutrons: These are neutral particles, also located inside the nucleus. These are responsible for most of the physical properties of an atom.
• Electrons: These are negatively charged atomic particles and are the only species that are located outside the nucleus. They revolve around the nucleus in definite circular orbits.
• Shells: These are the definite circular orbits in which the electrons are said to revolve around the nucleus. Every atom has a definite number of shells and every shell has a definite number of atoms.
The atoms in different shells also differ in their energies due to which, these shells are also referred to as energy levels.
Usually, the shell located at the least distance from the nucleus has the minimum energy, and the shell located at the maximum distance has the maximum energy.
These are named in alphabetical order as K, L, M, N, etc., or with the numerical value as 1, 2, 3, 4, etc., with the lowest value assigned to the shell closest to the nucleus.
The shell farthest from the nucleus is also known as the valence shell and the electrons housed in this shell as known as valence electrons. These electrons are responsible for the chemical bonding between atoms.
The electrons also jump from lower to higher or higher to lower orbits, depending on the energy gained or lost, respectively.
The phosphorous atom consists of 15 protons and 16 neutrons in the nucleus. 15 electrons revolve around the nucleus in 3 shells viz. K, L, and M shell.
|No. of Proton
|No. of Neutron
|Number of Electrons
|Number of shells
|Number of electrons in first (K) shell
|Number of electrons in second (L) shell
|Number of electrons in third (M) shell
|Number of valence electrons
Steps to Draw Bohr Model of Phosphorous
Phosphorous is a non-metallic chemical element that belongs to group 15 of the periodic table.
The information that can be derived from the above-mentioned phosphorous box is as follows:
• The atomic number of Phosphorous is 15.
• The electronic configuration of Phosphorous is [Ne] 3s23p3.
• The chemical symbol of Phosphorous is P.
• The atomic mass of Phosphorous is 30.97.
This information can now be used for drawing the Bohr model of the atom for phosphorous.
To begin with, we will first have to identify the atomic species for the Phosphorous atom.
Let us start with counting the number of protons inside the nucleus of the phosphorous atom.
The number of protons for any atom is always equal to the atomic number of that atom.
In the case of the Phosphorous atom, the atomic number is 15.
Therefore, for the Phosphorous atom, the number of protons = atomic number = 15
Moving forward, we will now calculate the number of neutrons for the phosphorous atom.
The formula used for calculating the number of neutrons in any atoms is given below:
Number of neutrons = Atomic mass (rounding it up to the nearest whole number) –
Number of protons
Now, we will use this formula for calculating the number of neutrons in the Phosphorous atom.
The atomic mass of phosphorous is 30.97. After rounding it up to the nearest whole number we will get 31.
Also, as calculated above, the number of protons in the phosphorous atom = 15
Now, put these values in the above formula to get your answer:
Number of neutrons = 31 – 15 = 16
Hence, the number of neutrons in the Phosphorous atom = 16.
We also learned in the previous section that the nucleus of an atom is constituted of neutrons and protons. Therefore, from the above values, we can now draw the nucleus of the Bohr model for the Phosphorous atom as given below:
In the above diagram, the p+ represents protons and n° represents neutrons.
Now, the only types of atomic particles, left to be accommodated in this atom, are the electrons. So, we will now calculate the number of electrons in the phosphorous atom.
For any atom, the number of electrons is always equal to the atomic number of that atom.
Therefore, in the case of the Phosphorous atom,
Number of electrons = Atomic number of Phosphorous = 15
Now, our next step would be accommodating these electrons in the shell surrounding the nucleus. But, for that, we first have to ascertain the number of electrons that can be housed in any particular shell.
The maximum number of electrons that can be housed in a particular shell is given by 2n2, where n refers to the number of shells.
We will now apply this formula to the phosphorous atoms, first, to calculate the number of electrons in its K shell.
For the K shell of the Phosphorous atom, the maximum number of electrons = 2 (1)2 = 2
We will now add these 2 electrons to the K shell of the Phosphorous atom which would now appear like this:
Once we are done with the K shell, we will now calculate the number of electrons for the L shell of the Phosphorous atom by applying the same formula:
The maximum number of electrons for the L shell of the Phosphorous atom = 2 (2)2 = 8
Therefore, the L shell can house 8 electrons.
However, one important point to be mentioned here is that in the Bohr model when a shell consists of more than four electrons, a definite pattern shall be followed for positioning the electrons in that shell.
Hence, the electrons from the L shell onwards will be added in the group of four, and also, all the four atoms will be placed, in a clockwise manner, at an angle of 90° from each other.
The remaining electrons will again be taken in the group of four, and added to the shell in a similar manner, except that this time the angle between the electrons becomes less than 90°.
Therefore, the first four electrons in the L shell of the Phosphorous atom will be positioned as follows:
After this, the remaining four electrons will also be added in a similar fashion. Therefore, after filling all the 8 electrons in the L shell, it would appear as follows:
Now, we are left with 3 more electrons that will be accommodated in the M shell of the Phosphorous atom.
Therefore, we will calculate the number of electrons that can be accommodated in the M shell.
The maximum number of electrons for M shell of the Phosphorous atom = 2 (3)2 = 18
This means that a total of 18 electrons can be housed in the M shell. However, we are only left with 3 electrons.
Therefore, these three electrons will now be housed in the M shell arranged in a clockwise manner. After which the final Bohr model of the Phosphorous atom would appear as follows:
Hence, the final Bohr model of an atom contains 15 protons and 16 neutrons in the nucleus while, 15 electrons revolve around the nucleus with 2 electrons in the K shell, 8 electrons in the L shell, and 3 electrons in the M shell.
Deriving Lewis Structure from Bohr Model
The Lewis structure of an atom is also the representation of the nucleus along with electrons. However, it differs from the Bohr model as only valence electrons are shown in the Lewis structure.
The nucleus of the atom is illustrated with the atomic symbol of the atom while the electrons are shown in the form of dots. Therefore, the Lewis structures are also known as electron dot structures.
As discussed in the above sections, the valence shell i.e. M shell of phosphorous comprises 3 electrons. Hence, the Lewis structure of phosphorous can be drawn as follows:
Properties of Phosphorous
A few important properties of Phosphorous are listed below:
• It is a nonmetal element of group 15.
• The density of phosphorous is 1.82 gm/ml at 20°C.
• The melting and boiling points of phosphorous are 44.2 °C and 280 °C, respectively.
• It is a reactive element that exists as red and white phosphorous.
Below is the video attached explaining how to draw a Bohr model diagram of a Phosphorus atom.
As per the Bohr model of the atom, the Phosphorous atom consists of 15 protons and 16 neutrons in the nucleus while 15 electrons revolve around the nucleus in 3 shells viz. K, L, and M shell.
The number of protons, as well as the number of electrons in an atom, is always equal to the atomic number of that atom.
The number of neutrons is given by the formula:
Number of neutrons = Atomic mass (rounding it up to the nearest whole number) – Number of protons
The maximum number of electrons that can be housed in a shell is given by the formula 2n2, where n is the number of shells.
The Phosphorous atom consists of three shells viz. K, L, and M shells have 2, 8, and 3 electrons, respectively.