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| | From:  Albert1145 (Original Message) | Sent: 3/21/2008 2:46 AM |
Hi I have a couple of questions, could you help me please:
Q1) When bonded to chlorine, which of the following atoms forms the bond with the greatest ionic character?
Al, K, P, C or Br
Q2) Based on electronegativities, which one of the following molecules would exhibit the greatest amount of ionic character in its bonds? ...My answer is N2, but I'm not sure
CaF2, CF4, N2, CH4, or CO2
Q3) Which one of the sp2 hybridised carbon atom in the following molecule has the most carbon atoms attached to it?
H3C-CH=CH2
Thank you and Happy Easter |
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| | | From: ·Steve· | Sent: 3/21/2008 6:34 AM |
The most ionic character in bonding results in compounds from the extreme left and right sides of the periodic table (excluding the noble gases). These will be compounds formed of metallic and nonmetallic elements. Question 3 �?It is good to first draw the structure showing all the bonds between the carbons and to each hydrogen. Then it is easy to tell how many carbons are bonded to such-and-such atom. Can you identify which carbon atom is sp3 hybridized and which two carbon atoms are sp2 hybridized? Let me know what you come up with on this one, and if need be, I can give you some pointers on identifying the hybridization of almost any atom.  Steve |
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Hi Steve,
My answer for question 3:
- the carbon on the left hand side is sp3
- the other two carbons are sp2 because the double bond is one sigma and one pi bond.
is that correct?
But I don't understand what it means by "which of the molecule has the most carbon atoms attached to it?"
And for question 1, do you mean whichever the atom that is closest to the sides of the periodic table has the greatest ionic character? What if I have potassium and bromine... which one is greater?
Thank you very much! |
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| | | From: ·Steve· | Sent: 3/21/2008 9:09 PM |
That is right about the hybridization of the carbons.
>> which of the molecule has the most carbon atoms attached to it <<
It wants to know which sp2 carbon atom has the most carbon atoms bonded to it (besides the carbon attached by the double bond). The sp2 carbon on the right side has two hydrogens bonded to it, but no other carbons (2H + double bond = 4 bonds on this carbon). The sp2 carbon in the middle has only 1H + 1C bonded to it, plus the double bond, also making 4 bonds on this carbon also. So, the middle alkene carbon atom has one other additional carbon atom attached to it, and the alkene carbon on the right has no additional carbon atoms attached to it.
In organic chemistry, there is a rule called Markovnikov's rule, which says that when a molecule "HX" adds to the double bond (and triple bond) in a reaction, the H atom adds to the alkene carbon which has the most hydrogens attached to it ("them that has, gets") and "X" adds to the other alkene carbon (the one with fewer hydrogens and more carbons attached to it). HX is a molecule such as HCl, HBr, HI, and H2O (you can think of H2O as "HOH" here).
> When bonded to chlorine, which of the following atoms forms the bond with the greatest ionic character? <<
In general, the greater the difference in electronegativities of the atoms, the more ionic the bond between them will be. So, the most ionic bond will be between elements which have the lowest and highest electronegativities. Elements having the lowest electronegativities are metals in the lower left side of the periodic table, and elements having the highest electronegativities are found in the upper right side of the table. There is a table of electronegativities here in the Documents folder, http://www.msnusers.com/ChemistryCorner/Documents/Table%20of%20Electronegativities%2Ehtm, which you can access when you are signed in. Look at this table to see the general trend. Your textbook should have a similar table also.
With the electronegativities, you can tell whether KCl or KBr will be more ionic. But you can tell without the table too, in this case. The only difference in these compounds is the halogen; the metal is the same. Which is more electronegative, Cl or Br? They are both in the same group, but Cl is nearer the top (closer to F, the most electronegative element). So, Cl is more electronegative than Br. That means that the difference in electronegativities of K and Cl is more than the difference between K and Br. Therefore, KCl is more ionic than KBr. Actually, KCl and KBr are both ionic compounds in terms of their chemical and physical properties, but strictly speaking, the bonding in KCl has more ionic character than in KBr.
Steve
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