<< Chapter < Page Chapter >> Page >

Key equations

  • bond order = ( number of bonding electron ) ( number of antibonding electrons ) 2

Chemistry end of chapter exercises

Sketch the distribution of electron density in the bonding and antibonding molecular orbitals formed from two s orbitals and from two p orbitals.

Got questions? Get instant answers now!

How are the following similar, and how do they differ?

(a) σ molecular orbitals and π molecular orbitals

(b) ψ for an atomic orbital and ψ for a molecular orbital

(c) bonding orbitals and antibonding orbitals

(a) Similarities: Both are bonding orbitals that can contain a maximum of two electrons. Differences: σ orbitals are end-to-end combinations of atomic orbitals, whereas π orbitals are formed by side-by-side overlap of orbitals. (b) Similarities: Both are quantum-mechanical constructs that represent the probability of finding the electron about the atom or the molecule. Differences: ψ for an atomic orbital describes the behavior of only one electron at a time based on the atom. For a molecule, ψ represents a mathematical combination of atomic orbitals. (c) Similarities: Both are orbitals that can contain two electrons. Differences: Bonding orbitals result in holding two or more atoms together. Antibonding orbitals have the effect of destabilizing any bonding that has occurred.

Got questions? Get instant answers now!

If molecular orbitals are created by combining five atomic orbitals from atom A and five atomic orbitals from atom B combine, how many molecular orbitals will result?

Got questions? Get instant answers now!

Can a molecule with an odd number of electrons ever be diamagnetic? Explain why or why not.

An odd number of electrons can never be paired, regardless of the arrangement of the molecular orbitals. It will always be paramagnetic.

Got questions? Get instant answers now!

Can a molecule with an even number of electrons ever be paramagnetic? Explain why or why not.

Got questions? Get instant answers now!

Why are bonding molecular orbitals lower in energy than the parent atomic orbitals?

Bonding orbitals have electron density in close proximity to more than one nucleus. The interaction between the bonding positively charged nuclei and negatively charged electrons stabilizes the system.

Got questions? Get instant answers now!

Calculate the bond order for an ion with this configuration:

( σ 2 s ) 2 ( σ 2 s * ) 2 ( σ 2 p x ) 2 ( π 2 p y , π 2 p z ) 4 ( π 2 p y * , π 2 p z * ) 3

Got questions? Get instant answers now!

Explain why an electron in the bonding molecular orbital in the H 2 molecule has a lower energy than an electron in the 1 s atomic orbital of either of the separated hydrogen atoms.

The pairing of the two bonding electrons lowers the energy of the system relative to the energy of the nonbonded electrons.

Got questions? Get instant answers now!

Predict the valence electron molecular orbital configurations for the following, and state whether they will be stable or unstable ions.

(a) Na 2 2+

(b) Mg 2 2+

(c) Al 2 2+

(d) Si 2 2+

(e) P 2 2+

(f) S 2 2+

(g) F 2 2+

(h) Ar 2 2+

Got questions? Get instant answers now!

Determine the bond order of each member of the following groups, and determine which member of each group is predicted by the molecular orbital model to have the strongest bond.

(a) H 2 , H 2 + , H 2

(b) O 2 , O 2 2+ , O 2 2−

(c) Li 2 , Be 2 + , Be 2

(d) F 2 , F 2 + , F 2

(e) N 2 , N 2 + , N 2

(a) H 2 bond order = 1, H 2 + bond order = 0.5, H 2 bond order = 0.5, strongest bond is H 2 ; (b) O 2 bond order = 2, O 2 2+ bond order = 3; O 2 2− bond order = 1, strongest bond is O 2 2+ ; (c) Li 2 bond order = 1, Be 2 + bond order = 0.5, Be 2 bond order = 0, strongest bond is Li 2 ;(d) F 2 bond order = 1, F 2 + bond order = 1.5, F 2 bond order = 0.5, strongest bond is F 2 + ; (e) N 2 bond order = 3, N 2 + bond order = 2.5, N 2 bond order = 2.5, strongest bond is N 2

Got questions? Get instant answers now!

For the first ionization energy for an N 2 molecule, what molecular orbital is the electron removed from?

Got questions? Get instant answers now!

Compare the atomic and molecular orbital diagrams to identify the member of each of the following pairs that has the highest first ionization energy (the most tightly bound electron) in the gas phase:

(a) H and H 2

(b) N and N 2

(c) O and O 2

(d) C and C 2

(e) B and B 2

(a) H 2 ; (b) N 2 ; (c) O; (d) C 2 ; (e) B 2

Got questions? Get instant answers now!

Which of the period 2 homonuclear diatomic molecules are predicted to be paramagnetic?

Got questions? Get instant answers now!

A friend tells you that the 2 s orbital for fluorine starts off at a much lower energy than the 2 s orbital for lithium, so the resulting σ 2 s molecular orbital in F 2 is more stable than in Li 2 . Do you agree?

Yes, fluorine is a smaller atom than Li, so atoms in the 2 s orbital are closer to the nucleus and more stable.

Got questions? Get instant answers now!

True or false: Boron contains 2 s 2 2 p 1 valence electrons, so only one p orbital is needed to form molecular orbitals.

Got questions? Get instant answers now!

What charge would be needed on F 2 to generate an ion with a bond order of 2?

2+

Got questions? Get instant answers now!

Predict whether the MO diagram for S 2 would show s-p mixing or not.

Got questions? Get instant answers now!

Explain why N 2 2+ is diamagnetic, while O 2 4+ , which has the same number of valence electrons, is paramagnetic.

N 2 has s-p mixing, so the π orbitals are the last filled in N 2 2+ . O 2 does not have s-p mixing, so the σ p orbital fills before the π orbitals.

Got questions? Get instant answers now!

Using the MO diagrams, predict the bond order for the stronger bond in each pair:

(a) B 2 or B 2 +

(b) F 2 or F 2 +

(c) O 2 or O 2 2+

(d) C 2 + or C 2

Got questions? Get instant answers now!

Questions & Answers

what is chemistry
Terhemba Reply
what is the difference between ph and poh?
Abagaro Reply
chemical bond that results from the attractive force between shared electrons and nonmetals nucleus is what?
Abagaro
what is chemistry
Ayok
what is chemistry
ISIYAKA Reply
what is oxidation
Chidiebube Reply
calculate molarity of NaOH solution when 25.0ml of NaOH titrated with 27.2ml of 0.2m H2SO4
Gasin Reply
what's Thermochemistry
rhoda Reply
the study of the heat energy which is associated with chemical reactions
Kaddija
How was CH4 and o2 was able to produce (Co2)and (H2o
Edafe Reply
explain please
Victory
First twenty elements with their valences
Martine Reply
what is chemistry
asue Reply
what is atom
asue
what is the best way to define periodic table for jamb
Damilola Reply
what is the change of matter from one state to another
Elijah Reply
what is isolation of organic compounds
IKyernum Reply
what is atomic radius
ThankGod Reply
Read Chapter 6, section 5
Dr
Read Chapter 6, section 5
Kareem
Atomic radius is the radius of the atom and is also called the orbital radius
Kareem
atomic radius is the distance between the nucleus of an atom and its valence shell
Amos
Read Chapter 6, section 5
paulino
Bohr's model of the theory atom
Ayom Reply
is there a question?
Dr
when a gas is compressed why it becomes hot?
ATOMIC
It has no oxygen then
Goldyei
read the chapter on thermochemistry...the sections on "PV" work and the First Law of Thermodynamics should help..
Dr
Which element react with water
Mukthar Reply
Mgo
Ibeh

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Chemistry' conversation and receive update notifications?

Ask