Lithium (Li) Electron Configuration

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Orbit Electron Configuration of Lithium (Li) atom is two electrons in first orbit (K) and 1 electron in second orbit (L)

Orbital Electron Configuration of Lithium (Li) atom is 1s2 2s1 which means Lithium atom have two electrons inside 1s orbital and one electron in 2s orbital

Li is the symbol for the element lithium, which is located at position three of the periodic table. Lithium has a total of three electrons in its atomic structure and it’s an Alkali Metal, therefore it’s an highly reactive element.

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 Lithium (Li) atom.

Orbit Electron Configuration of Lithium (Li)

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 Lithium atom have three electrons, therefore it’s Orbit Electron Configuration will be two electrons in K orbit and one electron in L orbit.

Orbit Electronic Configuration of Lithium is 2 and 1

Orbital Electron Configuration of Lithium (Li)

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 Lithium atom just have three electrons, therefore it’s electron configuration is 1s2 2s1.

Orbital Electronic Configuration of Lithium 1s1 2s1

Valence Electrons of Lithium (Li)

Number of electrons in the last orbit of an element’s atom are called valence electrons. As Lithium (Li) have electron configuration 1s2 2s1 so it’s last orbit is 2 (L shell which have Principle Quantum Number n = 2), as last orbit of Lithium have 1 electrons, therefore number of valence electrons in Lithium (Li) is one.

Lithium (Li)1 valence electron

Valency of Lithium (Li)

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 Lithium(Li) have electron configuration 1s2 2s1, which means orbital inside 1s subshell is fully filled and orbital inside 2s subshell have 1 one electron. Therefore Li atom is stable and don’t want to either gain or loose electrons. Thus, valency of Helium is zero. But orbital inside 2s subshell can have maximum of 2 electrons, but Li just have one electron in this orbital. So it can loose that electron to go from electron configuration 1s2 2s1 to 1s2 which is more stable.

Therefore valency of Lithium (Li) is one.

Lithium (Li)Valency = 1

How is valency of Lithium 1?

Valency refers to the ability of an element to combine with other elements.

Lithium atom has two shells K and L. K shell is fully filled with 2 electrons, but L shell have only one electron. Therefore Lithium can loose one electron to gain fully stable electron configuration (having 2 electrons in K shell).

As Lithium can loose one electron to become stable, therefore it’s valency is one.

Why Lithium is highly reactive? (based upon its electron configuration)

Lithium (Li) have electron configuration 1s2 2s1, which means orbital inside 1s subshell is fully filled and orbital inside 2s subshell is half filled. We know that if an orbital is half filled then it’s not in stable energy state as compared to state when it’s fully filled.

Therefore Lithium want to loose one electron in 2s subshell and achieve electron configuration 1s2. So lithium participate actively in reactions with other elements. For example – Lithium reacts aggressively with Oxygen to form Lithium Oxide.

Lithium (Li+) Electron Configuration

Above I discussed that in order to achieve stable electron configuration, in which all of orbitals are fully filled with electrons. Lithium want to loose its one electron in 2s orbital. But when an atom of Lithium does loose an electron, then number of protons(positive charge) and number of electrons(negative charge) becomes unequal.

Thus forming a Lithium (Li+) ion.

Li → Li+ + e

So Orbital Electron Configuration of Lithium (Li) atom is 1s2 2s1 and after one loosing one electron it becomes 1s2.
Therefore Electron Configuration of Lithium ion is 1s2.

Can Lithium loose 2 electrons?

Electron Configuration of Lithium (Li) is 1s2 2s1 and in order to achieve stable electron configuration, in which all of orbitals are fully filled with electrons. Lithium want to loose its one electron in 2s orbital.

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

Thus forming a Lithium (Li+) ion.

Li → Li+ + e

So Orbital Electron Configuration of Lithium (Li) atom is 1s2 2s1 and after one loosing one electron it becomes 1s2.

So now it we want to removed one more electron then that electron need to removed from 1s2 orbital which is fully filled and is stable. Therefore it’s not possible to remove 2 electrons from Lithium atom and form bi-positive lithium ion Li2+.

FAQs

What is electron configuration of neutral lithium?

Neutral lithium atom means that it have equal number of electrons and protons. As in neutral state Lithium atom have total three electrons, therefore it’s electron configuration is 1s2 2s1. Which means lithium atom have 2 electrons each in its 1s, 1 electron in 2s orbitals.

What is electron configuration of ground-state lithium 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 lithium atom just have 3 electrons, therefore it’s electron configuration is 1s2 2s1. Which means lithium atom have 2 electrons each in its 1s and just one electron in its 2s orbital.

What is electron configuration of lithium (Li+) ion?

When an atom of lithium loose 1 electron, then number of protons(positive charge) and number of electrons(negative charge) becomes unequal. Thus forming a lithium ion (Li+). As electron configuration of lithium atom is 1s2 2s1 and formation of lithium ion (Li+) require loosing of 1 electron therefore electron configuration of lithium ion is 1s2.

Which element have electron configuration 1s2 2s1?

Lithium (Li)

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

Electron configuration of magnesium is 1s2 2s1
From this it can be clearly observed that outermost electron in lithium atom is present in 2s orbital.

Some Anomalous Behaviour of Lithium

  • Very small size of lithium atom and its ones
  • Higher polarising power of Li+ resulting in increased covalent character of its compounds which is responsible for their solubility in organic solvents
  • Comparatively high ionisation enthalpy and low electropositive character of lithium as compared to other alkali metals
  • Strong inter metallic bonding
  • Lithium is harder while all other alkali metals are soft
  • Melting and boiling point of lithium are comparatively quite high as compared to other alkali metals

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