Boron (B) Electron Configuration

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Orbit Electron Configuration of Boron (B) atom is two electrons in first orbit (K) and 3 electron in second orbit (L)

Orbital Electron Configuration of Boron (B) atom is 1s2 2s2 2p1 which means Boron atom have two electrons inside 1s orbital, two electron in 2s orbital and 1 electron in 2p orbital

Also we can replace 1s2 with [He], therefore electron configuration of Boron (B) is [He] 2s2 2p1

B is the symbol for the element Boron, which is located at position five of the periodic table. Boron have total of five electrons in its atomic structure.

Electron configuration refers to the arrangement of electrons in different orbits and orbitals of an atom in a certain order. Depending upon whether electrons are being arranged in Orbits or Orbitals there are two types of electron configurations – Orbit Electron Configuration and Orbital Electron Configuration.

In this article, I’ve discussed both Orbit and Orbital Electron Configurations of Boron (B) atom.

Orbit Electron Configuration of Boron (B)

Niels Bohr, a Danish scientist, was the first to propose the concept of an orbit around an atom. In 1913, he presented a model of the atom to the scientific community. As per this model, the electrons in an atom follow a set path as they go around the nucleus in circular motion.

These set paths are called “Orbits” and are numbered as 1, 2, 3, ……… depending upon their closeness to nucleus of atom. So first circular path around nucleus is numbered as 1, second as 2 and so no. Moreover orbits are also denoted by English letters.

  • First orbit – K and have n = 1
  • Second orbit – L and have n = 2
  • Third orbit – M and have n = 3
  • Fourth orbit – N and have n = 4
  • and so on.

How many electrons any of these orbits can hold is determined by using formula 2n2 where n is number of orbit. Based upon this formula, different orbits in the atom can hold electrons as following.

  • First orbit – K (n = 1) can hold 2n2 = 2 (1)2 = 2 electrons
  • Second orbit – L and have n = 2 can hold 2n2 = 2 (2)2 = 2 (4) = 8 electrons
  • Third orbit – M and have n = 3 can hold 2n2 = 2 (3)2 = 2 (9) = 18 electrons
  • Fourth orbit – N and have n = 4 can hold 2n2 = 2 (4)2 = 2 (16) = 32 electrons
  • and so on.

As Boron atom have five electrons, therefore it’s Orbit Electron Configuration will be two electrons in K orbit and three electrons in L orbit.

Orbit Electronic Configuration of Boron B showing 2 electrons in K shell and 3 electrons in L shell

How many electron shells does Boron have?

Boron have electron configuration 2, 3 which means it have 2 electrons in K shell and 3 electrons in L shell. Therefore Boron have 2 electron shells.

Orbital Electron Configuration of Boron (B)

Niels Bohr proposed the idea that electrons revolve around nucleus in specific circular paths called Orbits, but later on Heisenberg found out that it’s impossible to determine position and velocity of an electron inside the atom at same time, so how it’s possible that electrons do circular motion on specific paths in an atom.

In later years, Erwin Schrodinger developed a mathematical formula to compute the probability of finding the location of an electron inside an atom.

On the basis of this probability, the location of an electron inside an atom could be represented as the chances of that electron being located in a certain three-dimensional area surrounding the nucleus.

As 3D region can be explained only using 3 parameters, therefore in order to describe where an electron is? inside the atom.

We need three numbers – Principle Quantum Number (n), Angular Momentum Number (l) and Magnetic Momentum Number (m).

Therefore Orbits(this concept was proposed by Neils Bohr) are further divided into sub-energy levels called subshells. How many subshells an orbit have is equal to Principle Quantum Number (n) of orbit.

Therefore

  • First Orbit (K and n = 1) have 1 subshell
  • Second Orbit (L and n = 2) have 2 subshell
  • Third Orbit (M and n = 3) have 3 subshell
  • Fourth Orbit (N and n = 4) have 4 subshell

These sub-energy levels/subshells have specific regions where probability of finding electrons is maximum. These subshells are names as s, p, d, f and have angular momentum numbers as 0, 1, 2 and 3 respectively.

Which type of subshell an orbit have can be determined using Angular Momentum Number (I).
So
If Principle Quantum Number of an orbit is n
Then subshells in that orbit are 0 to (n – 1)

If
Angular Momentum Number(l) = 0 that means it’s s orbital
Angular Momentum Number(l) = 1 that means it’s p orbital
Angular Momentum Number(l) = 2 that means it’s d orbital
Angular Momentum Number(l) = 3 that means it’s f orbital

First Orbit (K and n = 1)
Angular Momentum Number (l) = 0 to (1 – 1) = 0 (0 to 0)
Which means first orbit just have one subshell which is s

Second Orbit (L and n = 2)
Angular Momentum Number (l) = 0 to (2 – 1) = 1 (0 to 1)
Which means second orbit have two subshells which are s and p

Third Orbit (M and n = 3)
Angular Momentum Number (l) = 0 to (3 – 1) = 2 (0 to 2)
Which means third orbit have three subshells (0, 1, 2) which are s, p and d

Fourth Orbit (N and n = 4)
Angular Momentum Number (l) = 0 to (4 – 1) = 3 (0 to 3)
Which means fourth orbit have four subshells (0, 1, 2, 3) which are s, p, d and f

OrbitPrinciple Quantum NumberNumber of SubshellsSubshells
First Orbit (K)n = 111s
Second Orbit (L)n = 222s
2p
Third Orbit (M)n = 333s
3p
3d
Fourth Orbit (N)n = 444s
4p
4d
4f

These s, p, d and f subshells further have subregions which are called Orbitals, orbitals are just regions inside a subshell where probability of existence of an electron is quite high.

How many orbitals a subshell have depends upon it’s Angular Momentum Number (l) and can be calculated using formula.
Number of orbitals in a subshell = 2l + 1 where I is Angular Momentum Number of a subshell.

Therefore
s subshell (Angular Momentum Number l = 0)
Number of orbitals = 2(0) + 1 = 1
So s subshell just have one orbital

p subshell (Angular Momentum Number l = 1)
Number of orbitals = 2(1) + 1 = 3
So p subshell have three orbitals

d subshell (Angular Momentum Number l = 2)
Number of orbitals = 2(2) + 1 = 4 + 1 = 5
so d subshell have five orbitals

f subshell (Angular Momentum Number l = 3)
Number of orbitals = 2(3) + 1 = 6 + 1 = 7
so f subshell have seven orbitals

Moreover electron holding capacity of a subshell can be calculated using formula
Number of electrons which a subshell can hold = 2(2I + 1) where I is Angular Momentum Number of subshell

Therefore
s subshell (Angular Momentum Number l = 0)
Number of electrons it can hold = 2(2(0) + 1) = 2(1) = 2
So s subshell can hold maximum two electrons

p subshell (Angular Momentum Number l = 1)
Number of electrons it can hold = 2(2(1) + 1) = 2(3) = 6
So p subshell can hold maximum six electrons

d subshell (Angular Momentum Number l = 2)
Number of electrons it can hold = 2(2(2) + 1) = 2(4 + 1) = 2(5) = 10
so d subshell can hold maximum ten electrons

f subshell (Angular Momentum Number l = 3)
Number of electrons it can hold = 2(2(3) + 1) = 2(6 + 1) = 2(7) = 14
so f subshell can hold maximum fourteen electrons

SubshellAngular Momentum Number (I)Number of Orbitals in
Subshell (2l + 1)
Maximum Electrons Subshell can hold 2(2l + 1)
s012
p136
d2510
f3714

Summarising all this we can write energy levels in an atom as

1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f 5g

But next question which arises is “in which order these orbitals should be filled in to figure out electron configuration of an atom?”.

Like should 2 electrons be filled in 1s orbital first or 3p orbital first???

Well answer to this question is Aufbau Principle.

According to the Aufbau Principle, in the ground state of an ion or an atom, electrons first occupy the atomic orbitals of lowest energy levels before filling up in higher energy levels. What this indicates is that the orbital with the lower energy will be filled first, followed by the orbital with the greater energy.

As per this principle energy of any orbital depends upon sum of Principle Quantum Number (n) and Angular Quantum Number (l).
Therefore
Energy of Orbital = n + l

So lower the value of n + l is lower its energy.

OrbitalnIEnergy (n + l)
1s101
2s202
2p213
3s303
3p314
3d326
4s404
4p415
4d426
4f437

From the above table its clear that 4s have less energy than 3d, so it should be filled first.
Based upon the energies of orbitals as per Aufbau Principle, order of filling of orbitals is 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p 8s and so on.

It’s tricky to remember what’s order of filling of orbitals as per Aufbau Principle, so you can use below diagram for easily filling up orbitals. Just follow the arrows from top right corner to bottom left corner diagonally.

Order of filling orbitals in an atom as per Aufbau Principle
Aufbau Principle Filling Of Orbitals Order

Order of filling of orbitals as per Aufbau Principle is 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p 8s and so on.

As Boron atom have five electrons, therefore it’s electron configuration is 1s2 2s2 2p1. Which means Boron atom have 2 electrons each in its 1s, 2s orbitals and 1 electron in 2p orbital.

Orbital Electronic Configuration of Boron B showing electronic configuration of Boron as 1s2 2s2 2p1
BoronElectron Configuration
1s2 2s2 2p1

Valence Electrons of Boron (B)

Number of electrons in the last orbit of an element’s atom are called valence electrons.

As Boron have electron configuration 1s2 2s2 2p1 so it’s last orbit is 2 (L shell which have Principle Quantum Number n = 2), as last orbit of Boron have 3 electrons (2 in 2s and 1 in 2p subshell), therefore number of valence electrons in Boron is three.

Boron (B)3 valence electron

How many Valence Electrons does Boron have?

Boron have 4 electrons as it’s Orbital Electron Configuration is 1s1 2s2 2p1. As electron configuration shows, Boron have 3 valence electrons located in 2s and 2p subshells.

Why Boron lose 3 electrons?

Boron have electron configuration 1s2 2s2 2p1, there are 2 electrons in 2s subshell and 1 electron in 2p subshell but if Boron looses all three electrons in second orbit. Then its electron configuration becomes 1s2 which is electron configuration of Helium, a noble gas and therefore is more stable as compared to electron configuration of Boron (1s2 2s2 2p1).

Thus in order to become more stable, Boron easily looses 3 electrons and achieve more stable electron configuration of Helium.

Valency of Boron (B)

Valency refers to the ability of an element to combine with other elements. Valencies are same throughout the periodic table for elements that are located in the same group. 

Which means valency is same for all of Group 1 elements (K, Na etc. have valency = 1), Group 2 elements (Ca, Mg etc. have valency = 2) and so on for other groups in the periodic table. Also valency depends upon number of electrons that are found in an element’s outer most shell.

As Boron (B) have electron configuration 1s2 2s2 2p1, which means there are in total three electrons in 2s and 2p subshells.

Therefore B atom is not stable and want to loose three electrons in its second orbit and achieve more stable electron configuration 1s1.

Therefore valency of Boron (B) is three.

Boron (B)Valency = 3

Does Boron have Valency 3?

Valency refers to the ability of an element to combine with other elements and depends upon number of electrons available in most outermost shell of atom.

Boron atom has two shells K and L.
K shell is fully filled and L shell have 3 electrons, therefore Boron can loose three electrons to gain fully stable electron configuration of Helium (having 2 electrons in K shell).

As Boron can loose two electrons to become more stable, therefore it’s valency is three.

Boron (B3+) Electron Configuration

Above I discussed that in order to achieve stable electron configuration, in which all of orbitals are fully filled with electrons. Boron want to loose its three electrons in its second orbit (2 electrons in 2s and 1 electron in 2p).

But when an atom of Boron does loose three electrons, then number of protons(positive charge) and number of electrons(negative charge) becomes unequal.

Thus forming a Boron (B3+) ion.

B → B3+ + 3e

So Orbital Electron Configuration of Boron (B) atom is 1s2 2s2 2p1 and after loosing three electrons it becomes 1s2.
Therefore Electron Configuration of Boron (B3+) ion is 1s2.

Different Oxidation States of Boron

Oxidation State is defined as total number of electrons that an atom either gains or loses in order to form a chemical bond with another atom.

As I’ve discussed above electron configuration of Boron is 1s2 2s2 2p1. Just looking at this electron configuration its clear that Boron can loose or gain different number of electrons to achieve some stable noble gas electron configuration.

As Boron have capability to either loose/gain different number of electrons therefore it can have different Oxidation States in different compounds.

If Boron losses one electron (+ 1 Oxidation State)
Electron Configuration of Boron is 1s2 2s2 2p1 and if losses one electron then its electron configuration becomes 1s2 2s2 which is stable.

If Boron losses two electrons (+ 2 Oxidation State)
Electron Configuration of Boron is 1s2 2s2 2p1 and if losses two electrons then its electron configuration becomes 1s2 2s1.

If Boron losses three electrons (+ 3 Oxidation State)
Electron Configuration of Boron is 1s2 2s2 2p1 and if losses one electron then its electron configuration becomes 1s2.

If Boron gain one electron (- 1 Oxidation State)
Electron Configuration of Boron is 1s2 2s2 2p1 and if it gains one electron then its electron configuration becomes 1s2 2s2 2p2.

If Boron gain two electrons (- 2 Oxidation State)
Electron Configuration of Boron is 1s2 2s2 2p1 and if it gains one electron then its electron configuration becomes 1s2 2s2 2p3.

If Boron gain three electrons (- 3 Oxidation State)
Electron Configuration of Boron is 1s2 2s2 2p1 and if it gains one electron then its electron configuration becomes 1s2 2s2 2p4.

If Boron gain four electrons (- 4 Oxidation State)
Electron Configuration of Boron is 1s2 2s2 2p1 and if it gains one electron then its electron configuration becomes 1s2 2s2 2p5.

If Boron gain five electrons (- 5 Oxidation State)
Electron Configuration of Boron is 1s2 2s2 2p1 and if it gains one electron then its electron configuration becomes 1s2 2s2 2p6.

FAQs

What is electron configuration of neutral Boron?

Neutral Boron atom means that it have equal number of electrons and protons. As in neutral state Boron atom have total five electrons, therefore it’s electron configuration is 1s2 2s2 2p1. Which means boron atom have 2 electrons each in its 1s, 2s orbitals, 1 electron in 2p orbitals.

What is electron configuration of ground-state Boron atom?

Ground state atom means that all electrons inside it are in least possible energy state levels, therefore net total energy of atom in ground-state is minimum out of all possible states of it. As boron atom just have 5 electrons, therefore it’s electron configuration is 1s2 2s2 2p1. Which means boron atom have 2 electrons each in its 1s, 2s orbitals, 1 electron in 2p orbitals.

What is electron configuration of Boron (B3+) ion?

When an atom of boron looses 3 electrons, then number of protons(positive charge) and number of electrons(negative charge) becomes unequal. Thus forming a Boron Ion (B3+). As electron configuration of Boron atom is 1s2 2s2 2p1 and formation of boron ion (B3+) require loosing of 3 electrons therefore electron configuration of boron ion is 1s2.

Which element have electron configuration 1s2 2s2 2p1?

Boron (B)

In what type of orbital is the outermost electron in Boron?

Electron configuration of Boron is 1s2 2s2 2p1
From this it can be clearly observed that outermost electron in boron atom is present in 2p orbital.

Some Properties of Boron

Element NameBoron
SymbolB
Atomic Number5
Number of electrons5
Group in Periodic Table15
Atomic Weight10.811 u
Number of Valence Electrons3
Valency3
First Ionisation Energy800.6 kJ/mol
Second Ionisation Energy2427.1 kJ/mol
Third Ionisation Energy3659.7 kJ/mol
Oxidation States– 5, -1, 0, 1, 2, 3
Melting Point2349 K
Boiling Point4200 K
Atomic Radius85 picometre
Electronegativity2.04 eV
Covalent Radius110 picometre
Van der waals Radius192 picometre

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