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Molecular orbital (MO) diagram for Ne2, Ne2+, Ne22+, and their bond order

Does Ne2 exist? Is it a stable molecule? If so, what is its bond order, and how to calculate it? If all these questions intrigue you, then you must be looking for the molecular orbital (MO) diagram of Ne2. The good news is – you have hit the right spot.

In this article, you will find a step-by-step guide on drawing the Molecular orbital diagrams of Ne2, Ne2+, and Ne22+. We will also teach you to write the MO electronic configuration of each of the above species, calculate their bond orders, and determine their magnetic properties.

So, for all that and much more continue reading the article.

Name of molecule

Diatomic neon (Neon dimer)

Chemical formula

Ne2

Electronic configuration

1s2 2s2 2p6

Molecular orbital electronic configuration

(σ1s2 )(σ*1s2) (σ2s2)(σ*2s2) (σ2pz2)(π2px2)(π2py2) (π*2px2) (π*2py2) (σ*2pz2)

Number of electrons in bonding MOs

10

Number of electrons in anti-bonding MOs

10

Bond order

0

Paramagnetic or Diamagnetic?

Diamagnetic 

 

How to draw the molecular orbital (MO) diagram of Ne2 with its bond order?

As per the molecular orbital theory (MOT) of chemical bonding, after bond formation, the individual atomic orbitals cease to exist. Rather, the atomic orbitals of constituent atoms combine to form a unique set of molecular orbitals (MOs).

The electrons of the participant atoms are thus held in these MOs, belonging to the entire molecule in unison.

The linear combination of atomic orbitals (LCAO) produces two types of molecular orbitals:

  • Bonding molecular orbitals
  • Anti-bonding molecular orbitals

The number of MOs produced is exactly equal to the number of atomic orbitals coming together.

A bonding molecular orbital (BMO) is formed by the linear combination of two AOs in the same phase.

Contrarily, an antibonding molecular orbital (ABMO) is produced by the linear combination of two AOs in the opposite phase, counteracting the cohesive forces of the combining nuclei.

formation of bonding and antibonding Molecular orbital diagram (MO) for Ne2

This is why, a bonding MO always lies at a lower energy (greater stability) than the parent AOs while an antibonding MO occupies an energy level higher than that of parent AOs (higher instability).

The electrons are filled in these MOs following the three simple rules:

  1. Aufbau Principle: Electrons first occupy the lower energy orbitals followed by their placement in the higher energy molecular orbitals.
  2. Hund’s Rule: The incoming electrons are singly filled in the degenerate MOs before pairing occurs.
  3. Pauli Exclusion Principle: Two electrons placed in the same MO exhibit an opposite spin (clockwise and anticlockwise).

The different numbers of electrons present in the bonding and/or antibonding MOs of a molecule are displayed schematically on an energy level diagram called the molecular orbital (MO) diagram.

The formula Ne2 represents a homonuclear diatomic molecule i.e., a molecule containing two atoms from the same element, in this case, a Noble gas element, neon (Ne) from Group VIII A (or 18) of the Periodic Table.

You can easily draw the Molecular orbital diagram of Ne2 following the simple steps given below.

Steps for drawing the molecular orbital (MO) diagram of Ne2 with its bond order

1. Write down the electronic configuration of Ne2 atoms

Ne2 comprises two identical neon (Ne) atoms.

The electronic configuration of each Ne-atom is 1s2 2s2 2p6.

Usually, only the valence electrons are displayed in the MO diagram of a molecule, therefore, it is important to note that each Ne-atom contains 8 valence electrons.

2 Ne-atoms combined make a total of 2(10) = 20 electrons and 2(8) = 16 valence electrons to be filled in the Molecular orbital diagram of Ne2.

2. Determine whether the molecule is homonuclear or heteronuclear

Ne2 is a neutral molecule. It is homonuclear as it is formed by two atoms of the same element.

As per the rule of LCAO, the two 1s atomic orbitals of neon overlap to produce two molecular orbitals i.e., a bonding molecular orbital (σ1s) and an antibonding molecular orbital (σ*1s).

Similarly, two 2s atomic orbitals combine to form two MOs, σ2s and σ*2s. Finally, the three 2p atomic orbitals from each Ne-atom overlap to produce six MOs including three bonding MOs (σ2pz, π2px, and π2py) and three anti-bonding MOs (π*2px, π*2py, and σ*2pz).

The MOs discussed above are located on the MO diagram in an increasing energy order.

energy level diagram of Ne2

3. Fill the molecular orbitals of Ne2 with electrons following the energy and bonding principles

A total of 4 electrons are present in the 1s atomic orbitals of two neon atoms. Therefore, as per the Aufbau principle, the first two electrons go in the lowest energy σ1s MO, and the remaining two are accommodated in σ*1s.

Similarly, the 4 electrons in the 2s atomic orbitals of neon, are uniformly distributed between σ2s and σ*2s molecular orbitals of Ne2.

In contrast, there are a total of 6 + 6 = 12 electrons in the 2p atomic orbitals of two Ne-atoms.

These electrons are filled in the Molecular orbital diagram of Ne2 as follows:

  • 2 electrons occupy σ2pz as an electron pair.
  • The next 2 electrons are first singly filled in the π2px and π2py MOs (Hund’s rule). These are then paired up in an opposite spin (Pauli Exclusion Principle).
  • The 2p antibonding MOs (π*2px and π*2py) are then filled with a total of 4 electrons, 2 each in the same manner.
  • The last 2 electrons occupy the highest energy level σ*2pz.

In this way, we obtain the correct Molecular orbital diagram of Ne2, completely filled with electrons, as shown below.

Molecular orbital diagram (MO) of Neon (Ne2) and it's bond order

As per the above diagram, the Molecular orbital electronic configuration of Ne2 is-

(σ1s2) (σ*1s2) (σ2s2) (σ*2s2) (σ2pz2) (π2px2) (π2py2) (π*2px2) (π*2py2) (σ*2pz2)

Is Ne2 diamagnetic or paramagnetic?

Ne2 is a diamagnetic molecule as there are no unpaired electrons in its molecular orbital diagram.

Diamagnetic substances possess no permanent dipole moment value; therefore they get repelled by an external magnetic field.

Bond order of Ne2

The bond order formula is:

bond order formula for Ne2

∴ Bond order = (Nb –Na)/2

  • Nb = Electrons present in the bonding MOs (Bonding electrons).

∴ Electrons in σ1s + σ2s + σ2pz + π2px + π2py = 2 + 2 + 2 + 2+ 2 = 10

  • Na= Electrons present in the anti-bonding MOs (Anti-bonding electrons).

∴ Electrons in σ*1s + σ*2s + π*2px + π*2py + σ*2pz = 2 + 2 + 2 + 2 +2 = 10

Bond order of Ne2 = (10 – 10)/2 = 0/2 = 0. 

A bond order of zero means Ne2 is an extremely unstable molecule. It is rather a hypothetical (imaginary) molecule that does not exist in real life.

Neon (Ne) is a Noble gas element, inert in nature. It does not react with itself or other elements to gain stability; rather it is very stable on its own possessing a full outer shell electronic configuration i.e., a complete octet (8 valence electrons).  

MO diagrams and bond orders of Ne2+ and Ne22+

Ne2+ represents a cation of the neon dimer. It is a molecular ion formed by the loss of 1 valence electron from Ne2.  

This valence electron is removed from one of the three 2p orbitals of an individual Ne-atom.

20 – 1 results in a total of 19 electrons to be filled in the Molecular orbital diagram of Ne2+.

Thus, upon Ne2+ formation, the electron present in the highest energy σ*2pz MO gets unpaired. As a result, Ne2+ is paramagnetic and its Molecular orbital diagram is as shown below:

Ne2+ Molecular orbital diagram (MO) and Bond order

∴ Bond order of Ne2+ = (Nb –Na)/2 = (10 – 9)/2 = 0.5  

Molecular orbital electronic configuration of Ne2+: (σ1s2) (σ*1s2) (σ2s2) (σ*2s2) (σ2pz2) (π2px2) (π2py2) (π*2px2) (π*2py2) (σ*2pz1).   

Paramagnetic

On the other hand, Ne22+ is formed by removing two electrons, one from a 2p AO of each Ne-atom.

20-2  results in a total of 18 electrons to be filled in the MO diagram of Ne22+.

Therefore, both the electrons present in σ*2pz MO of Ne2 get unpaired, producing the Ne22+ MO diagram.

The absence of any unpaired electron reveals the diamagnetic nature of Ne22+.

∴ Bond order of Ne22+ = (Nb –Na)/2 = (10 – 8)/2 = 1

Molecular orbital electronic configuration of Ne22+: (σ1s2) (σ*1s2) (σ2s2) (σ*2s2) (σ2pz2) (π2px2) (π2py2) (π*2px2) (π*2py2).

Diamagnetic

Ne22+ Molecular orbital diagram (MO) and Bond order

Bond strength, stability, and bond lengths of Ne2, Ne2+, and Ne22+

Both Ne2+ and Ne22+ ions possess bond order values greater than zero. This means these molecular ions are relatively more stable than the parent molecule i.e., Ne2. Ne2+ and Ne22+ thus exist in real life. However, Ne22+ is more stable than Ne2+.

The bond order signifies the strength of a bond. Therefore, for the Ne2 family, the bond strength increases as follows:

Ne2 < Ne2+ < Ne22+

On the contrary, bond order is inversely proportional to bond length. The greater the bond strength, the closer the bonded atoms are to each other, i.e., possessing a shorter bond length.  

Therefore, the suspected bond lengths of the Ne2 family follow the reverse order:

Ne2 > Ne2+ > Ne22+

Also read:

FAQ

What is the molecular orbital diagram for Ne2?

The molecular orbital (MO) diagram of Ne2 is shown below.

What is the molecular orbital diagram for Ne2

The MO electronic configuration of Ne2 is

(σ1s2) (σ*1s2) (σ2s2) (σ*2s2) (σ2pz2) (π2px2) (π2py2) (π*2px2) (π*2py2) (σ*2pz2)

There are no unpaired electrons in the Molecular orbital diagram of Ne2; therefore, it is diamagnetic in nature.

The bond order of Ne2 is zero, which means it is an extremely unstable, hypothetical molecule.

What is the bond order of Ne2?

The bond order of Ne2 is calculated as follows:

Bond order = (Nb – Na)/2

= (10-10)/2 = 0

Thus, the bond order of Ne2 is zero.

By using the molecular orbital theory, why doesn’t the Ne2 molecule exist? 

As per the molecular orbital theory (MOT), there are an equal number of electrons in the bonding and antibonding molecular orbitals of Ne2.

Thus, the bond order of Ne2 is zero hence it is extremely unstable and does not exist in real life.

Which out of the three is paramagnetic, Ne2, Ne2+, or Ne22+?

There is an unpaired electron in the Molecular orbital diagram of Ne2+, therefore it is paramagnetic. Contrarily, both Ne2 and Ne22+ are diamagnetic species, containing no unpaired electrons.

How many unpaired electrons are there in the MO diagrams of Ne2, Ne2+, and Ne22+

There are 2 unpaired electrons in the MO diagram of Ne2+ while Ne2 and Ne22+ contain no unpaired electrons.

How is the Molecular orbital diagram of F2 different from that of Ne2?

The MO electronic configuration of F2 is (σ1s2) (σ*1s2) (σ2s2) (σ*2s2) (σ2pz2) (π2px2) (π2py2) (π*2px2) (π*2py2) while that of Ne2 is (σ1s2) (σ*1s2) (σ2s2) (σ*2s2) (σ2pz2) (π2px2) (π2py2) (π*2px2) (π*2py2) (σ*2pz2).

Their MO diagrams are shown below.

Both F2 and Ne2 are diamagnetic molecules. However, the bond order of F2 is 1 while that of Ne2 is 0.

Therefore, F2 is a stable molecule, made up of two F-atoms, joined together via a single covalent bond. Its MO diagram is similar to that of Ne22+.

Contrarily, Ne2 is extremely unstable and thus does not exist in reality.

MO diagram of Ne2

MO diagram of F2

Which out of Ne2, Ne2+, and Ne22+ is the most stable and possesses the shortest bond length?

Ne22+ is the most stable out of all three discussed above, as it has the highest bond order.

As bond length is inversely proportional to bond stability therefore Ne22+ possesses the shortest bond length as well.  

Summary

  • Ne2 represents a homonuclear diatomic molecule, containing two identical Ne-atoms.
  • The MO electronic configuration of Ne2 is (σ1s2) (σ*1s2) (σ2s2) (σ*2s2) (σ2pz2) (π2px2) (π2py2) (π*2px2) (π*2py2) (σ*2pz2).
  • The absence of any unpaired electron in the Molecular orbital diagram of Ne2 predicts its diamagnetic nature.   
  • The bond order of Ne2 is zero, which means Ne2 is extremely unstable and does not exist in real.
  • Ne2+ and Ne22+ are molecular ions formed by the loss of electrons from the valence shell atomic orbitals of individual Ne-atoms.
  • The bond order follows the ascending pattern: Ne2 < Ne2+ < Ne22+ i.e., 0, 0.5, and 1 respectively.
  • Ne2+ is paramagnetic while both Ne2 and Ne22+ are diamagnetic in nature.
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Vishal Goyal author of topblogtenz.com

Vishal Goyal is the founder of Topblogtenz, a comprehensive resource for students seeking guidance and support in their chemistry studies. He holds a degree in B.Tech (Chemical Engineering) and has four years of experience as a chemistry tutor. The team at Topblogtenz includes experts like experienced researchers, professors, and educators, with the goal of making complex subjects like chemistry accessible and understandable for all. A passion for sharing knowledge and a love for chemistry and science drives the team behind the website. Let's connect through LinkedIn: https://www.linkedin.com/in/vishal-goyal-2926a122b/

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