How Many Valence Electrons Does Silicon (Si) Have? [Valency of Silicon]

Silicon, a chemical element with the symbol Si and atomic number 14, is a crystalline solid with a blue-grey metallic luster. According to the Pauli scale, its electronegativity value is 1.90 and it can show characteristics of both metals and non-metals (metalloid). Its oxides show an amphoteric nature as its oxidation states exhibit -4, -3, -2, -1, 0, +1, +2, +3, +4.

Silicon with 96.5% - 99.5% purity can be made by reducing quartzite or sand with highly purified coke. The reduction process takes place in presence of excess SiO2 which helps to stop the production of silicon carbide (SiC).

SiO₂ + 2 C → Si + 2 CO

2 SiC + SiO₂ → 3 Si + 2 CO

You are here to know valence electrons of the silicon atom, aren’t you? Don’t worry along with silicon valence electrons we will explain its valency also. But before that let’s have some basic ideas about what these two terms are:

Difference Between Valence Electrons and Valency

Valence electrons are the total number of electrons present in the outermost shell of an atom (i.e. in outermost orbital). The valence electrons for a neutral atom are always definite, it cannot be varied (more or less) in any condition for a particular atom and may or may not be equal to its valency.

Valency is defined as the total number of electrons an atom can lose, gain, or share at the time of bond formation to get a stable electronic configuration i.e. to complete an octet. The valency of an atom can be variable in different compounds or chemical reactions due to the different bonding circumstances. Most of the time valency varies/changes due to change in oxidation and reduction states.

Silicon (Si) Valence Electrons

There are four simple steps to find out the valence electrons for silicon atom which are:

Step 1: Find the Atomic Number

To find out the atomic number of silicon, we can use the periodic table. With the help of the periodic table, we can easily see that the atomic number of silicon is 14. As its atomic number is 14, it has 14 protons, and for neutral silicon, the number of protons are always equal to the number of electrons i.e. has 14 electrons in its nucleus.

Step 2: Write Electron Configuration

Electron configuration is the arrangement of electrons on the orbitals. The silicon atom has a total of 14 electrons so, we have to put 14 electrons in orbitals. The electrons will be placed in different orbitals according to the energy level: [1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f]. Now,

Silicon electron configuration Si (14) =  1s22s22p63s23p2 (complete configuration).

=  [Ne] 3s²3p² (condensed configuration).

Step 3: Determine Valence Shell

As we know, the valence shell of an atom can be found from the highest number of principle quantum numbers which are expressed in the term of n, and in [Ne] 3s²3p², the highest value of n is 3 so that the valence shell of silicon is 3s²3p².

Step 4: Find Valence Electrons

The total number of electrons present in the valence shell of an atom are called valence electrons, and there are a total of four electrons present in the valence shell of silicon (3s²3p²). Thus, silicon has four valence electrons.

Valency of Silicon (Si)

There are many different ways to find out the valency of an atom which reflects the ability of an atom to bond with other atoms. Valence describes how easily an atom or a free radical can combine with other chemical species. The valency of an atom is determined based on the number of electrons lost, gained, or shared with another atom at the time of bond formation.

An atom is said to be stable when its outermost shells have eight electrons (except H & He). If the total number of electrons in outermost shells is between one to four, the atom has positive valency and if electrons are between four to eight, the valency is calculated by subtracting from eight and valency will be zero. Atoms having four outermost electrons possess both positive and negative valency, and atoms having eight outermost electrons, valency will be zero (i.e. noble gases).

Elements like silicon can reach the stable state (nearest inert gas configuration) either by losing 4 outermost electrons or by gaining 4 electrons. So that the valency of silicon is 4 (tetravalency).

Note: Silicon has both +4 & -4 valency states. If it loses three electrons to reach a stable state (i.e. He), its valency will be +4. But if it gains five electrons to reach a stable state (i.e. Ne), its valency will be -4 as explained above.

In another sense, a silicon atom can form four covalent bonds in chemical bonding (For example SiF4, SiH4, SiCl4, etc.), and that what valency is, the maximum ability to form bonds with different atoms at the time of chemical reactions.

We can also find the valency of silicon with the help of the periodic table. As silicon belongs to group 14 (IVa) along with carbon (C), germanium (Ge), tin (Sn), lead (Pb), and flerovium (Fl). All these elements have a valency state of four (tetravalent).

Clarification: Valency is the combining capacity of an element at the time of chemical bonding. so that valency cannot be negative or positive, it is just a number value between 0 to 4.