Very simple polar covalent bond questions

1. Jan 6, 2005

nemzy

polar covalent bonds occur because one atom is much more electronegative than the other right?

so..an example of a polar covalent bond is C-H ?

2. Jan 6, 2005

lucifer

not necessarily much more... if the differnce in electronegativity is too high the bond is likely ionic but within covalent bonds polar covalent bonds is basically "unfair sharing" while in ionic bonds theres no sharing. a c-h bond is polar covalent but not that polar. but a H-F bond is prolly as polar you can get within covalent bonds.

3. Jan 6, 2005

DB

This should be under chemistry, but the answer to your first question is yes, the stronger the electronegative force, the more likely the atom is to form a bond, that is, it is more reactive. Water is polar covalent, Oxygen needing only 2 electrons to stabilize its outer shell, so it takes 2 electrons from 2 hydrogen atoms leaving just 2 protons (though it's covalent not ionic so they are still sharing electrons)

C-H would not react like so. $$C-H_4$$ is what would happen, with Carbon acting like a metal (carbon is a metalloid) and Hydrogen acting as a gas. Carbon has 6 protons so its nucleus charge is 6+ a greater charge than Hydrogen 1+, so it is more electronegative. But in this case it still needs 4 electrons to fill its outer shell. This is because a full 2nd energy level ($$2s^2 2p^6$$) has 8 electrons. That is when 8 are in its second energy level, it is stable and inert. Carbon $$2s^22p^2$$ only has 4 (2+2, the exponent says how many electrons are in that shell) so it needs 4 more, therefore it takes 4 from hydrogen making a covalent molecule. Because it is tetrahedronal it will not be as polar as water.
So in order to make carbon tetrahydride you would need 4 times as much hydrogen then carbon.

4. Jan 6, 2005

chem_tr

Hello, acetone ($\displaystyle (H_3C)_2-C=O$) is a good example for polar covalent bonds. In this compound, a polar C=O group is present, in which there are sufficiently different electronegativities of the participating atoms. As other friends said, C-H bond is not very polar, so alkanes are the least polar groups, but acetone is much more polar than alkanes.

Last edited: Jan 6, 2005
5. Jan 6, 2005

Gokul43201

Staff Emeritus
Any bond between two dissimilar atoms is polar.

The greater the difference in electronegativity and the larger the atoms, the greater is the polarity (or dipole moment). The electronegativity difference between C and H is nearly the smallest it can be among any pair. Also, both atoms are tiny. So, in fact, such a bond has a fairly low polarity.

Still, there is some non-negligible polarity in this bond, which plays an important role in organic reactions via what are known as +R and +I effects.