How Many Valence Electrons Does Boron (B) Have? [Valency of Boron]

Boron, a chemical element with the symbol B and atomic number 5, is a low-abundance element found in the solar system. It is a non-metallic element with a black-brown appearance. It has mainly two naturally occurring and stable isotopes which are 11B (80.1%), and 10B (19.9%).

Borax (Na2[B4 O5(OH)4].8H2O), orthoboric acid (H3BO3), diborane (B2H6), Boron trifluoride (BF3), Borane (BH3) are some of the common compounds of boron. Boron normally does not react with air at room temperature, but at higher temperatures, it started burning and forms boron trioxide.

4 B + 3 O₂ → 2 B₂O₃

You are here to know valence electrons of a boron atom, aren’t you? Don’t worry along with boron 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 is 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.

Boron (B) Valence Electrons

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

Step 1: Find the Atomic Number

To find out the atomic number of boron, we can use the periodic table. With the help of the periodic table, we can easily see that the atomic number of boron is 5. As its atomic number is 5, it has five protons, and for neutral boron, the number of protons are always equal to the number of electrons i.e. has five electrons in its nucleus.

Step 2: Write Electron Configuration

Electron configuration is the arrangement of electrons on the orbitals. The boron atom has a total of five electrons so, we have to put 5 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,

Boron electron configuration B (5) =  1s22s22p1 (complete configuration).

= [He] 2s22p1 (condensed configuration).

Step3: 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 [He] 2s22p1, the highest value of n is 2 so that the valence shell of B is 2s22p1.

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 three electrons present in the valence shell of boron (2s22p1). Thus, the boron has three valence electrons.

Valency of Boron (B)

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 boron can reach the stable state (nearest inert gas configuration) by losing 3 outermost electrons or by getting 5 electrons. So that the valency of boron (B) is 3.

Note: Boron has both +3 & -3 valency states. If it loses three electrons to reach a stable state i.e. He, its valency will be +3. But if it gains five electrons to reach a stable state i.e. Ne, its valency will be -3 as explained above.

As we know boron is a non-metallic element so that is an electromotive and for electromotive elements losing an electron is not a good option. This is the reason why boron has -3 valency most of the time.

We can also find the valency of boron with the help of the periodic table. As boron belongs to group IIIa along with aluminum, gallium, indium, thallium, and nihonium. And these all elements possess a valency state of three.

Boron is better known as metalloid as it can show characteristics of both metals and nonmetals. When boron reacts with high electropositive atoms like sodium or potassium, it acts as a non-metal. But when it reacts with lower electronegative atoms like fluorine, it behaves like metal and forms BF3 (Boron trifluoride).