Iodine Electron Configuration: I⁻ Ion, Orbital, Valency

Iodine is the 53th element in the periodic table and the symbol is ‘I’. Iodine has an atomic number of 53, which means that its atom has 53 electrons around its nucleus.

The electron configuration of iodine is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁵, which means that the first two electrons enter the 1s orbital. Since the 1s orbital can hold only two electrons, the next two will enter the 2s orbital. The next six electrons enter the 2p subshell. The p subshell can hold a maximum of six electrons. So first we put six electrons in the 2p subshell and then the next two electrons in the 3s orbital.

Since the 3s is now full, the electrons will move to the 3p subshell, where the next six electrons will enter. The 3p subshell is now full. Consequently, the following two electrons will enter the 4s orbital. Since the 4s orbital is full, the next ten electrons will move into the 3d subshell. The d subshell can hold a maximum of ten electrons. So, the next six electrons will enter the 4p subshell.

Since the 4p is full, the next two electrons will move to the 5s orbital. The 5s orbital is now full. Consequently, the next ten electrons will enter the 4d subshell. Since the 4d is full, the remaining five electrons will enter the 5p subshell. Hence, the electron configuration of iodine will be 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁵.

The electron configuration of iodine refers to the arrangement of electrons in the iodine atom’s orbitals. It describes how electrons are distributed among the various atomic orbitals and energy levels, and provides a detailed map of where each electron is likely to be found.

To understand the mechanism of iodine electron configuration, you must understand two basic things. These are orbits and orbitals. Also, you can arrange electrons in those two ways. In this article, I have discussed all the necessary points to understand the mechanism of iodine electron configuration. I hope this will be helpful in your study.

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Electron arrangement of Iodine through the Bohr model

The atomic number is the number of electrons in that element. The atomic number of iodine is 53. That is, the number of electrons in iodine is fifty-three. Therefore, an iodine atom will have two electrons in the first shell, eight in the 2nd orbit, and eighteen electrons in the 3rd shell.

According to Bohr’s formula, the fourth shell will have twenty-five electrons but the fourth shell of iodine will have eighteen electrons and the remaining seven electrons will be in the fifth shell. Therefore, the order of the number of electrons in each shell of the iodine(I) atom is 2, 8, 18, 18, 7.

Electron configuration of Iodine through orbital

Atomic energy shells are subdivided into sub-energy levels. These sub-energy levels are also called orbital. The most probable region of electron rotation around the nucleus is called the orbital.

The sub-energy levels depend on the azimuthal quantum number. It is expressed by ‘l’. The value of ‘l’ is from 0 to (n – 1). The sub-energy levels are known as s, p, d, and f.

Orbit Number	Value of ‘l’	Number of subshells	Number of orbitals	Subshell name	Electrons holding capacity	Electron configuration
1	0	1	1	1s	2	1s2
2	0 1	2	1 3	2s 2p	2 6	2s2 2p6
3	0 1 2	3	1 3 5	3s 3p 3d	2 6 10	3s2 3p6 3d10
4	0 1 2 3	4	1 3 5 7	4s 4p 4d 4f	2 6 10 14	4s2 4p6 4d10 4f14

Explanation:

• If n = 1,
  (n – 1) = (1–1) = 0
  Therefore, the value of ‘l’ is 0. So, the sub-energy level is 1s.
• If n = 2,
  (n – 1) = (2–1) = 1.
  Therefore, the value of ‘l’ is 0, 1. So, the sub-energy levels are 2s, and 2p.
• If n = 3,
  (n – 1) = (3–1) = 2.
  Therefore, the value of ‘l’ is 0, 1, 2. So, the sub-energy levels are 3s, 3p, and 3d.
• If n = 4,
  (n – 1) = (4–1) = 3
  Therefore, the value of ‘l’ is 0, 1, 2, 3. So, the sub-energy levels are 4s, 4p, 4d, and 4f.
• If n = 5,
  (n – 1) = (n – 5) = 4.

Therefore, l = 0,1,2,3,4. The number of sub-shells will be 5 but 4s, 4p, 4d, and 4f in these four subshells it is possible to arrange the electrons of all the elements of the periodic table.

Sub-shell name	Name source	Value of ‘l’	Value of ‘m’ (0 to ± l)	Number of orbital (2l+1)	Electrons holding capacity 2(2l+1)
s	Sharp	0	0	1	2
p	Principal	1	−1, 0, +1	3	6
d	Diffuse	2	−2, −1, 0, +1, +2	5	10
f	Fundamental	3	−3, −2, −1, 0, +1, +2, +3	7	14

The orbital number of the s-subshell is one, three in the p-subshell, five in the d-subshell, and seven in the f-subshell. Each orbital can have a maximum of two electrons.

The sub-energy level ‘s’ can hold a maximum of two electrons, ‘p’ can hold a maximum of six electrons, ‘d’ can hold a maximum of ten electrons, and ‘f’ can hold a maximum of fourteen electrons.

Aufbau is a German word, which means building up. The main proponents of this principle are scientists Niels Bohr and Pauli. The Aufbau method is to do electron configuration through the sub-energy level.

The Aufbau principle is that the electrons present in the atom will first complete the lowest energy orbital and then gradually continue to complete the higher energy orbital.

The energy of an orbital is calculated from the value of the principal quantum number ‘n’ and the azimuthal quantum number ‘l’. The orbital for which the value of (n + l) is lower is the low energy orbital and the electron will enter that orbital first.

Orbital	Orbit (n)	Azimuthal quantum number (l)	Orbital energy (n + l)
3d	3	2	5
4s	4	0	4

Here, the energy of 4s orbital is less than that of 3d. So, the electron will enter the 4s orbital first and enter the 3d orbital when the 4s orbital is full. Following the Aufbau principle, the sequence of entry of electrons into orbitals is 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p.

Therefore, the complete electron configuration for iodine should be written as 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁵.

Note: The unabbreviated electron configuration of iodine is [Kr] 4d¹⁰ 5s² 5p⁵. When writing an electron configuration, you have to write serially.

Excited state electron configuration of Iodine

Atoms can jump from one orbital to another orbital in an excited state. This is called quantum jump. The ground state electron configuration of iodine is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁵.

In the iodine ground-state electron configuration, the last electrons of the 5p orbital are located in the 5p_x(2), 5p_y(2) and 5p_z orbitals. We already know that the p-subshell has three orbitals. The orbitals are p_x, p_y, and p_z and each orbital can have a maximum of two electrons.

Then the correct electron configuration of iodine in ground state will be 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p_x² 5p_y² 5p_z¹. This electron configuration shows that the last shell of the iodine atom has an unpaired electron. So the valency of iodine is 1.

When iodine atoms are excited, the iodine atoms absorb energy. As a result, an electron in the 5p_y orbital jumps to the 5d_xy orbital. We already know that the d-subshell has five orbitals. The orbitals are d_xy, d_yz, d_zx, d_x²-y² and d_z² and each orbital can have a maximum of two electrons.

Therefore, the electron configuration of iodine(I*) in an excited state will be 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p_x² 5p_y¹ 5p_z¹ 5d_xy¹. Here, iodine has three unpaired electrons. In this case, the valency of iodine is 3.

When iodine is further excited, then an electron in the 5p_x orbital jumps to the 5d_yz orbital. Therefore, the electron configuration of iodine(I**) in an excited state will be 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p_x¹ 5p_y¹ 5p_z¹ 5d_xy¹ 5d_yz¹. Here, iodine has five unpaired electrons. So in this case, the valency of iodine is 5.

When iodine is further excited, then an electron in the 5s orbital jumps to the 5d_zx orbital. Therefore, the electron configuration of iodine(I***) in an excited state will be 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s¹ 5p_x¹ 5p_y¹ 5p_z¹ 5d_xy¹ 5d_yz¹ 5d_zx¹. Here, iodine has seven unpaired electrons. In this case, the valency of iodine is 7.

From the above information, we can say that iodine exhibits variable valency. Due to this, the oxidation states of iodine are 1, 3, 5, 7. The iodine atom exhibits -1, +1, +3, +5, +7 oxidation states. The oxidation state of the element changes depending on the bond formation.

Iodide ion(I^–) electron configuration

After arranging the electrons, it is seen that the last shell of the iodine atom has seven electrons. Therefore, there are seven valence electrons of iodine. The elements that have 5, 6, or 7 electrons in the last shell receive the electrons in the last shell during bond formation.

The element that receives electrons and forms a bond is called anion. During the formation of a bond, the last shell of iodine receives an electron and turns into an iodide ion(I^–). Therefore, iodide is an anion element.

I + e^– → I^–

Here, the electron configuration of iodide ion(I^–) is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶. This electron configuration shows that the iodide ion(I^–) has five shells and the last shell has eight electrons. The electron configuration shows that the iodide ion(I^–) has acquired the electron configuration of xenon and it achieves a stable electron configuration.