Flag Physical Chemistry> chemical bonding...
question mark

Which of the following orbitals of a diatomic molecule AB will not have positive overlap?

1) 2S(A) and 2S(B) 2) 2S(A) and 2Px(A) 3) 2Px(A) and 2Px(B) 3) 2S(A) and 2Pz(B)

bala sankar , 12 Years ago
Grade Upto college level
anser 1 Answers
Aman Bansal

Last Activity: 12 Years ago

Dear Bala,

Note that we''re not taking energy differences into account. In cases where the difference in orbital energy is greater than 15eV you get negligible overlap. Now onto the symmetry-allowed overlaps.

1s and 2s are both spherical and overlap to form a sigma bond.

1s and 2p(x) form a sigma bond. You can tell because if you draw the 2p(x) lobe you''ll see it overlap with the corresponding 1s.

The 2p(x) and the 2p(y) do not overlap. There is no possible bond. Draw the 2p(x) extending toward the other atom as positive or shaded (remember: positive does not denote charge). The other atom has its 2p(y) pointing up and down (perpendicular) and there is equal positive and negative overlap, thus canceling both of them out. No net overlap.

3p(y)-3p(y) form a pi bond. Once again, draw these out and see it for yourself. Draw the 3p(y) orbitals as rather fat so you can see how they overlap. Since they are not cylindrically symmetric they are not a sigma bond. Pretend you were to rotate one of the atoms about the x-axis... you would change orientation and there''d be less overlap. For the sigma bonds above, rotation does not affect the overlap.

2p(x)-2p(x) have positive overlap. Draw them and see why. They point toward one another. Moreover, if you rotate one of the 2p(x) orbitals about the x-axis you keep the same structure/orientation since the 2p(x) is along the x-axis. Thus, you can tell that this gives a sigma bond.

Cracking IIT just got more exciting,It s not just all about getting assistance from IITians, alongside Target Achievement and Rewards play an important role. ASKIITIANS has it all for you, wherein you get assistance only from IITians for your preparation and win by answering queries in the discussion forums. 

http://www.askiitians.com/packages/packages.aspx

So start the brain storming…. become a leader with Elite Expert League ASKIITIANS

Thanks

Aman Bansal

Askiitian Expert


star
LIVE ONLINE CLASSES

Prepraring for the competition made easy just by live online class.

tv

Full Live Access

material

Study Material

removal

Live Doubts Solving

assignment

Daily Class Assignments