Silicon Electron Configuration and Atomic Orbital Diagram

Silicon is the 14th element in the periodic table and the symbol is ‘Si’. Silicon’s atomic number is 14, which means its atom has fourteen electrons around its nucleus.

The electron configuration of silicon is 1s² 2s² 2p⁶ 3s² 3p², which means that the first two electrons enter the 1s orbital. Since the 1s orbital can hold only two electrons, the next two enter the 2s orbital. The next six electrons enter the 2p subshell. The p subshell can hold a maximum of six electrons. Hence, the next two electrons enter the 3s orbital. Since the 3s orbital is now full, the remaining two electrons move into the 3p orbital. Therefore, the electron configuration of silicon will be 1s² 2s² 2p⁶ 3s² 3p².

The electron configuration of silicon refers to the arrangement of electrons in the silicon 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 silicon electron configuration, you need to 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 silicon electron configuration and excited state electron configuration, and valency of silicon. I hope this will be helpful in your study.

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Electron arrangement for Silicon through Bohr Model

The atomic number is the number of electrons in that element. Silicon is a semiconductor material. The atomic number of silicon is 14. That is, the number of electrons in silicon is fourteen. Therefore, the silicon atom will have two electrons in the first shell, eight in the 2nd orbit, and four electrons in the 3rd shell. Therefore, the order of the number of electrons in each shell of a silicon atom is 2, 8, 4.

Electron configuration of silicon through Aufbau Model

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 silicon should be written as 1s² 2s² 2p⁶ 3s² 3p².

Note: The unabbreviated electron configuration of silicon is [Ne] 3s² 3p². When writing an electron configuration, you have to write serially.

How to write the orbital diagram for silicon?

Orbital diagrams are usually represented by boxes. Each box represents an orbital and the arrows within the box represent the position of the electron. The boxes are arranged in order of energy of the orbitals.

The lowest energy orbitals are closest to the nucleus and the higher energy orbitals are progressively further away from the nucleus in order of their energy levels. To write the orbital diagram of silicon, you have to write the orbital notation of silicon. Which has been discussed in detail above.

1s is the closest and lowest energy orbital to the nucleus. Therefore, the electrons will first enter the 1s orbital. According to Hund’s principle, the first electron will enter 1s orbital in the clockwise direction and the next electron will enter the 1s orbital in the anti-clockwise direction.

The 1s orbital is now filled with two electrons. The next two electrons will enter the 2s orbital just like the 1s orbital. The next three electrons will enter the 2p orbital in the clockwise direction and the next three electrons will enter the 2p orbital in the anti-clockwise direction.

The 2p orbital is now full. Then the next two electrons will enter the 3s orbital just like the 1s orbital and the remaining two electrons will enter the 3p orbital in the clockwise direction. This is clearly shown in the figure of the orbital diagram of silicon.

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Excited state electron configuration for Silicon

Atoms can jump from one orbital to another in an excited state. This is called a quantum jump. The ground state electron configuration of silicon is 1s² 2s² 2p⁶ 3s² 3p². 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.

In the silicon ground-state electron configuration, the two electrons of the 3p orbital are located in the p_x and p_y orbitals and the spin of the two electrons is the same. Then the correct electron configuration of silicon in the ground state will be 1s² 2s² 2p⁶ 3s² 3p_x¹ 3p_y¹.

This electron configuration shows that the last shell of the silicon atom has two unpaired electrons. So the valency of silicon is 2. When silicon atoms are excited, silicon atoms absorb energy.

As a result, an electron in the 3s orbital jumps to the 3p_z orbital. The second orbit of the silicon atom is filled with electrons. So, the electron of the third orbit jumps and goes to another orbital of the third orbit.

So, the electron configuration of silicon(Si*) in an excited state will be 1s² 2s² 2p⁶ 3s¹ 3p_x¹ 3p_y¹ 3p_z¹. The valency of the element is determined by electron configuration in the excited state. This electron configuration shows that the last shell of the silicon atom has four unpaired electrons. In this case, the valency of silicon is 4.