Bohr model of Iodine Atom-How to draw Iodine (I) Bohr-Rutherford diagram?

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The Bohr Model of Iodine (I) has a nucleus that contains 74 neutrons and 53 protons. This nucleus is surrounded by five electron shells namely K-shell, L-shell, M-shell, N-shell, and O-shell. The 1st shell has 2 electrons, the 2nd shell has 8 electrons, the 3rd shell has 18 electrons, the 4th shell also has 18 electrons and the 5th shell has 7 electrons.  

NameIodine Bohr Model
Number of neutrons74
Number of protons53
Number of electrons53
Total electron shells5
Electron in the First shell(K)2
Electrons in the Second shell(L)8
Electrons in the Third shell(M)18
Electrons in the Fourth shell(N)18
Electrons in the Fifth shell(O)7
Total valence electrons in Iodine7

How to draw Bohr Model of Iodine (I)?

Bohr model describes the visual representation of orbiting electrons around the small nucleus. It used different electron shells such as K, L, M, N…so on. These shells hold a specific number of electrons, the electron shell which is closest to the nucleus has less energy and the electron shell which is farthest from the nucleus has more energy.

Bohr’s diagram is very interesting and easy to draw. Here, we will draw the Bohr model of the Iodine atom with some simple steps.

Steps to draw the Bohr Model of Iodine atom

1. Find the number of protons, electrons, and neutrons in the Iodine

Protons are the positively charged particles and neutrons are the uncharged particles, both these are constituents of the atom nuclei. Electrons are the negatively charged particles that orbit the nucleus of an atom

To find the number of protons an atom contains, just look at its atomic number.

If the atomic number of atom is 45, then proton will also be 45, if atomic number is 46, then proton will also be 46.

So, the atomic number for Iodine is 53, hence, the number of protons in the Iodine atom is also 53.

number of protons in iodine atom

Now, to determine the number of neutrons in an atom, use this formula.

⇒ Number of neutrons in atom = Atomic mass of the atom(rounded to the nearest whole number) – Number of proton in an atom

For example, An atom have 33.988 atomic mass and 16 protons.

Then, to find the number of neutron, round the atomic mass to the near whole number, so, atomic mass 33.988 round to 34.

= (34 – 16 protons) = 18 number of neutrons in the atom

Now, To get the number of neutrons in an Iodine atom, look at its atomic mass which is 126.90 rounded to 127, and the number of protons in Iodine is 53.

∴ Hence, the number of neutrons in Iodine atom = (127 – 53) = 74

number of neutrons in iodine bohr diagram

It should be noted that “The number of electrons in a neutral atom is equal to the number of protons”.

As the Iodine (I) atom is neutral thus the number of electrons present in it will be equal to its number of protons i.e., 53, as we discussed earlier.

⇒ The number of electrons in an Iodine atom = 53

⇒ The number of protons in the Iodine atom = 53

⇒ The number of neutrons in an Iodine atom = 74

Let’s read in detailHow to find number of protons, electrons, neutrons?

2. Draw the nucleus of an atom

A nucleus is a dense and small region that contains the number of protons and neutrons of an atom.

In this step, we have to draw a small circle that consists of a number of protons and the number of neutrons of an Iodine atom.

nucleus in bohr model of iodine

3. Draw the First electron shell

“An electron shell may be thought of as an orbit followed by electrons around an atom’s nucleus.”

The first electron shell is also called the K-shell, this is the closest shell to the nucleus of an atom and can hold a maximum of two electrons.

As we identified, the Iodine atom has a total of 53 electrons. So we need to put 2 electrons from the 53 available in the first shell, next to each other, as shown below.

1st electron shell of iodine

Now, that we have successfully drawn the first shell of the Iodine atom that can hold 2 electrons, we know that we have used 2 electrons out of the 53 available in the first shell.

(53-2) = 51 electrons.

This shows we are left with 51 electrons that we need to accommodate in the subsequent shells of the Iodine atom.

4. Draw the Second electron shell

The second shell also called the L-shell that can hold a maximum of 8 electrons. This shell is drawn after the first electron shell.

In the second electron shell, the electrons are added one at a time, starting from the top position and then going in a clockwise direction.

In second shell, electrons are added one at a time in clockwise direction as a clock position – 12 o’clock, 3 o’clock, 6 o’clock, 9 o’clock positions.

electrons placing position in bohr diagram

Once you place the electrons one at a time to each of the four sides(Top – Right – Bottom – Left], start pairing or doubling them.

As we have 51 remaining electrons of an Iodine atom, out of which the second shell can hold only a maximum of 8 valence electrons.

Thus, we place the next 8 electrons of the Iodine atom in the second shell. Start from the top position and put electrons one at a time, moving in a clockwise direction (Top-Right-Bottom-Left), and finally pair them up.

2nd electron shell in iodine bohr diagram

At this step, out of the 53 electrons of the Iodine atom, we have placed 2 electrons in the first shell and 8 electrons in the second shell.

[53 – (2+8)] = 43 electrons.

This means we are now left with 43 electrons. So let’s see how we can assign them their appropriate positions in the next shells of the Iodine atom.

5. Draw the Third electron shell

The third electron shell also called the M-shell can accommodate up to 18 electrons. For the elements in the first few periods of the Periodic Table, the third shell holds up to 8 electrons only. But actually, in totality, it has the capacity to hold 18 electrons.

⇒ The third subshell exhibits this capacity of holding ‘up to 18’’ electrons for atomic numbers greater than 20 such as 21,22,23,24, 25, 26, and so on.

⇒ The atomic number of iodine (I) is 53. As 53 is visibly greater than 20, this means the M-shell in the iodine Bohr model will be filled to its maximum capacity by accommodating a total of 18 electrons, as shown below.

The electrons are placed in a clockwise manner, as we discussed in step 4. Starting from the top position, put the electrons one at a time while moving in a clockwise direction (Top-Right—Bottom-Left), before pairing up the electrons.

3rd electron shell of iodine atom

43 – 18 = 25.

28 electrons are now used up till this step out of the 53 available for drawing the Bohr model of iodine. This leaves behind 25 electrons. Let’s see how we can use these 25 electrons in the next electron shells to obtain an accurate Iodine Bohr model.

6. Draw the Fourth electron shell

The fourth electron shell i.e., N-shell has a maximum capacity of holding 32 electrons in total. It consists of s, p, d, and f subshells.

The s subshell can contain 2 electrons, 6 electrons can be placed in the p-subshell, 10 electrons can be placed in the d-subshell while a total of 14 electrons can be accommodated in the f-subshell of shell number 4. 2+6+10+14 makes a total of 32 electrons.

⇒ But the twist here is that the electrons are placed in these subshells according to the Aufbau principle. The electrons are filled diagonally. The s and p subshells of shell number 5 are filled prior to filling the d and f subshells of shell number 4 respectively. The electrons are filled in the order of 4p, 5s, 4d, 5p, and then 4f.

aufbau principle for filling electrons in iodine bohr model

According to this rule, the 4th shell in the iodine atom only has a total of 18 electrons because 7 electrons go to shell number 5 as per the distribution of two electrons in 5s and five electrons in 5p.  

As all the electrons get used up by the time the 5p subshell is filled therefore shell number 4 cannot reach its maximum capacity of holding 32 electrons in the Iodine atom.

In short, 18 electrons are placed in the fourth electron shell in the iodine Bohr model. The clockwise electron filling order i.e., top-right-bottom-left is strictly followed here as well.

4th electron shell of iron bohr diagram

25 – 18 = 7.

Thus these 7 electrons are consequently put into the fifth electron shell, as discussed in the next step.

7. Draw the Fifth electron shell

The 7 remaining electrons of Iodine are placed into the Fifth electron shell, again in a clockwise manner.

fifth electron shell of iodine bohr model

Now, the 5th shell has a total of 7 electrons.

Bohr model of iodine (I)

Finally, you have the Bohr model of the Iodine atom that contains 53 protons and 74 neutrons in the nucleus region while a total of 53 electrons circulate around the nucleus in specific orbits called shells.

The first electron shell of Iodine has two electrons, there are eight electrons in the second shell, eighteen electrons in each of the third and fourth electron shells, and seven electrons are present in the fifth shell of the Iodine atom.

Also Read:-

Also check :- Bohr model for all elements of Periodic table


What is the Bohr diagram?

The Bohr diagram formally called a Bohr-Rutherford model is a visual representation of orbiting electrons around the small nucleus of an atom. For example, the Bohr diagram of Iodine (I) represents the 53 electrons present in it, revolving around the small nucleus in specific energy levels called K, L, M, N, and O shells.

How many electron shells an Iodine Bohr model contains?

Electron shells are also called energy levels. You can find the number of electron shells for an element by knowing its period number in the Periodic Table.

The elements or atoms in the first period of the Periodic Table have one energy level or one electron shell, similarly, the elements in the second period have two energy levels or two electron shells, and so on.

As the iodine (I) atom belongs to the 5th Period in the periodic table, hence the number of electron shells for the Bohr model of Iodine is also 5. There are 5 electron shells in the Iodine Bohr model namely K-shell, L-shell, M-shell, N-shell, and O-shell.

What is the outer shell of the Bohr diagram of the Iodine atom?  

The outermost shell also called the valence shell is the shell that contains the valence electrons of an atom.

According to the Bohr diagram of Iodine, its outer shell is shell number 5 i.e., the O-shell containing 7 valence electrons. So, there are 7 valence electrons present in an atom of iodine (I).


  • The Bohr model of Iodine (I) is drawn with five electron shells, the first shell contains 2 electrons, the second shell contains 8 electrons, the third and fourth shells contain 18 electrons each and the fifth shell contains 7 electrons.
  • The atomic number of Iodine is 53. As Iodine (I) is a neutral atom hence the number of protons and electrons available for its Bohr diagram are equal i.e., 53.
  • The number of neutrons for the Bohr diagram of Iodine can be found by subtracting the number of protons from the atomic mass (rounded off to the nearest whole number).
  • The electron configuration of Iodine in terms of the shells is [2, 8, 18, 18, 7] while in the standard form it is [Kr] 4d10 5s2 5p5.

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Vishal Goyal is the founder of Topblogtenz, a comprehensive resource for students seeking guidance and support in their chemistry studies. He holds a degree in B.Tech (Chemical Engineering) and has four years of experience as a chemistry tutor. The team at Topblogtenz includes experts like experienced researchers, professors, and educators, with the goal of making complex subjects like chemistry accessible and understandable for all. A passion for sharing knowledge and a love for chemistry and science drives the team behind the website. Let's connect through LinkedIn:

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