Oxygen (O) Electron Configuration

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Orbit Electron Configuration of Oxygen (O) atom is two electrons in first orbit (K) and 6 electrons in second orbit (L)

Orbital Electron Configuration of Oxygen (O) atom is 1s2 2s2 2p4 which means Oxygen atom have two electrons inside 1s orbital, two electron in 2s orbital and 4 electrons in 2p orbitals

Moreover as 2p subshell have orbitals 2px, 2py and 2pz therefore Orbital Electron Configuration of Oxygen (O) can be written as
1s2 2s2 2px2 2py1 2pz1
or
1s2 2s2 2px1 2py2 2pz1
or
1s2 2s2 2px1 2py1 2pz2

Also we can replace 1s2 with [He], therefore electron configuration of Oxygen (O) is [He] 2s2 2p4

O is the symbol for the element Oxygen, which is located at top of group 18 of the periodic table. Oxygen have total of eight electrons in its atomic structure. Almost 20% of earth’s atmospheric volume is just oxygen gas, not only that it’s most vital gas for Humans. Because human body use this gas to extract energy out of food that we eat, therefore life on earth is made possible by Oxygen.

Existence of Oxygen was discovered by Joseph Priestly in 1774.

Talking about its properties it is a colorless, odorless, tasteless gas and is highly reactive (forms oxides with most of elements). One of major application of it is that it support combustion. Which means it can be used for burning things.

Some other most common uses of Oxygen are cutting and welding metals, steel production, using in explosives along with charcoal and as an oxidant for rocket fuel.

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 Oxygen (O) atom.

Orbit Electron Configuration of Oxygen (O)

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 Oxygen atom have eight electrons, therefore it’s Orbit Electron Configuration will be two electrons in K orbit and six electrons in L orbit.

How many electron shells does Oxygen have?

Oxygen have electron configuration 2, 6 which means it have 2 electrons in K shell and 6 electrons in L shell. Therefore Oxygen have 2 electron shells.

How many electrons does Oxygen have in K shell?

2 electrons

How many electrons does Oxygen have in L shell?

6 electrons

Orbital Electron Configuration of Oxygen (O)

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 Oxygen atom have eight electrons, therefore it’s electron configuration is 1s2 2s2 2p4. Which means Oxygen atom have 2 electrons each in its 1s, 2s orbitals and 4 electrons in 2p orbitals.

Electron Configuration of Oxygen Atom showing 1s2 2s2 2p4
NitrogenElectron Configuration
1s2 2s2 2p4

How do you write the electron configuration for Oxygen?

Oxygen atom in total have eight electrons, to write down the electron configuration of oxygen, the first two electrons would go into the 1s orbital. Because the 1s orbital can only accommodate two electrons, next two electrons are placed in the 2s orbital. The remaining four electrons would go in the 2p subshell orbitals. Putting all this together, electron configuration of nitrogen is 1s2 2s2 2p4. Which can also be written as [He] 2s2 2p4 where [He] represents electron configuration of noble gas Helium.

How many orbitals are in Oxygen Atom?

Electron Configuration of nitrogen atom is 1s2 2s2 2p4 which means
Oxygen Atom have
– 2 electrons in 1s subshell
– 2 electrons in 2s subshell
– 4 electrons in 2p subshell

Distribution of electrons in Orbitals of Oxygen Atom showing 2 electrons in 1s, 2 electrons in 2s and 4 electrons in 2p

1s subshell have just one orbital
2s subshell also just have one orbital
2p subshell have 3 orbitals

So in total nitrogen atom 1 + 1 + 3 = 5 orbitals

Therefore oxygen atom have 5 orbitals.

Valence Electrons of Oxygen (O)

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

As Oxygen have electron configuration 1s2 2s2 2p4 so it’s last orbit is 2 (L shell which have Principle Quantum Number n = 2), as last orbit of Oxygen have 6 electrons (2 in 2s and 4 in 2p subshell), therefore number of valence electrons in Oxygen is six.

Oxygen (O)6 valence electron

How many Valence Electrons does Oxygen have?

Oxygen have 6 valence electrons as it’s Orbital Electron Configuration is 1s2 2s2 2p4. As electron configuration shows, Oxygen have 6 valence electrons located in 2s and 2p subshells.

How many electrons does Oxygen require to reach an octet in it’s valence shell?

Electron configuration of oxygen in terms of shells is 2, 6 which means it have 2 electrons in K shell and 6 electrons in L shell. Though maximum capacity of L shell is to accomodate 8 electrons. Therefore if oxygen accepts 2 electrons then it’s configuration become 2, 8 and it’s L shell become full (as there are 8 electrons in L shell that’s why its called Octet).

Therefore in order to reach an octet in it’s valence shell Oxygen need to gain 2 electrons.

Valency of Oxygen (O)

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 Oxygen (O) have electron configuration 1s2 2s2 2p4, which means there are in total five electrons in outermost subshell (2s and 2p subshells).

Oxygen usually combines with other elements by gaining or sharing electrons. In both cases, oxygen either share 2 of its 2p electrons with other atoms to form covalent double bond or gains 2 electrons to become oxide (O2-) ion.

In both of these cases, Oxygen achieves more stable electronic configuration of Neon noble gas (1s2 2s2 2p6)

Therefore valency of Oxygen (O) is 2.

Oxygen (O)Valency = 2

Does Oxygen have Valency 1?

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

Oxygen atom has two shells K and L.
Its electron configuration is 1s2 2s2 2p4 and therefore it can either share or gain 2 electrons to achieve more stable electron configuration of nearest noble gas Neon (1s2 2s2 2p6). As Oxygen just need 2 electrons therefore valency of oxygen is 2 instead of 1.

Oxygen Anion or Oxide (O2-) Electron Configuration

Above I discussed that in order to achieve stable electron configuration, in which all of orbitals are fully filled with electrons. Oxygen want to gain 2 electrons in 2p orbitals and achieve electron configuration of Neon noble gas.

But when an atom of Oxygen does again 2 electrons, then number of protons(positive charge) and number of electrons(negative charge) becomes unequal.

Thus forming an Oxide (O2-) ion. Which have 2 electrons more than number of protons.

O + 2e → O2-

Orbital diagram showing Formation of Oxide Ion from Oxygen Atom

So Orbital Electron Configuration of Oxygen (O) atom is 1s2 2s2 2p4 and after gaining two electrons it becomes 1s2 2s2 2p6.
Therefore Electron Configuration of Oxide (O2-) ion is 1s2 2s2 2p6.

Electron Configuration of Oxide Ion showing 1s2 2s2 2p6

Summary

Electron Configuration of Oxygen is 1s2 2s2 2p4
Electron Configuration of Oxide Ion (O2-) is 1s2 2s2 2p6

FAQs

What is Valency of Oxygen?

Oxygen usually combines with other elements by gaining or sharing electrons. In both cases, oxygen either share 2 of its 2p electrons with other atoms to form covalent double bond or gains 2 electrons to become oxide (O2-) ion. Therefore valency of Oxygen (O) is 2.

Why is the valency of oxygen 2 and not 6?

The number of electrons in Oxygen is 8 and it’s electron configuration is 2, 6.
It either shares or gains 2 electrons to achieve 8 electrons in its outermost shell to complete the octet and become stable. Hence the valency of oxygen is 2 instead of 6.

What is electron configuration of neutral oxygen?

Neutral Oxygen atom means that it have equal number of electrons and protons. As in neutral state Oxygen atom have total eight electrons, therefore it’s electron configuration is 1s2 2s2 2p4. Which means oxygen atom have 2 electrons each in its 1s, 2s orbitals, 4 electrons in 2p orbitals.

What is electron configuration of ground-state oxygen 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 oxygen atom just have 8 electrons, therefore electron configuration of ground-state oxygen atom is 1s2 2s2 2p4. Which means oxygen atom have 2 electrons each in its 1s, 2s orbitals, 4 electrons in 2p orbitals.

What is electron configuration of oxide ion (O2-)?

When an atom of oxygen gains 2 electrons, then number of protons(positive charge) and number of electrons(negative charge) becomes unequal. Thus forming a Oxide Ion (O2-). As electron configuration of Oxygen atom is 1s2 2s2 2p4 and formation of oxide ion (O2-) require gaining of 2 electrons therefore electron configuration of oxide ion is 1s2 2s2 2p6.

Some Properties of Oxygen

Element NameOxygen
SymbolO
Atomic Number8
Number of electrons8
Group in Periodic Table18
Atomic Weight15.999 u
Number of Valence Electrons6
Valency2
Oxidation States– 1
– 2
Melting Point54.36 K
Boiling Point90.188 K
Atomic Radius56 picometre
Electronegativity3.44 on Pauling Scale
Van der waals Radius152 picometre
First Ionisation Energy1313.9 kJ/mol
Second Ionisation Energy3388.3 kJ/mol
Third Ionisation Energy5300.5 kJ/mol
Covalent Radius0.74 Å
Electron Affinity– 142 kJ/mol
Density0.001308 g cm-3

Some Uses of Oxygen

Glass and stone goods, as well as mining, all make utilise oxygen.
In the event of excessive pressure, special oxygen chambers are used to boost the concentration of oxygen around the patient.
Other metals or alloys, such as steel, may be refined and manufactured using oxygen as a major energy source.

Some Physical Properties of Oxygen

The gas is colourless, odourless and tasteless in a normal state. Liquid oxygen is slightly paramagnetic. It is reactive and forms oxides with every element except noble gases. It is moderately soluble in water.
Dioxygen is one of the common allotropes of oxygen.
Trioxygen (Ozone O3) is the most reactive allotrope of oxygen that can cause damage to lung tissue.

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