What does it mean for a bond to be the "most polar" bond in a group?
97857
Yeah, it's the greatest electronegativity difference between the two atoms that are forming that bond.  In other words, it's the difference between how far away the two elements are from fluorine, the most electronegative element.  Diatomic molecules like Cl2 are very nonpolar because both Cl atoms are equidistant from fluorine, and HBr is more polar because Br is closer to fluorine than hydrogen.
452453
No, we don't use the electronegativity chart; instead we draw the full structure of the molecule and then see which 'pulling of bonds' cancel each other. \nIn the molecule AsF3, since As has 5 outer most electrons(in group 5), each F is bonded to As with a single covalent bond. Hence, the shape of the molecule becomes trigonal pyramidal, with 3 bond pairs (with 3 F atoms) and 1 lone pair. The 3 bond pairs pull the electrons towards themselves in the lower plane, while the 1 lone pair pulls at the top. The pulling effect of the 2 F atoms at the 2 sides cancel out  because the pulling effect is the same for both F atoms; however, the pulling effect of the lone pair at the top and the 1 F bond pair at the bottom will not cancel, because it is not from the same atom/species. Hence the overall dipole moment( dipole moment = charge x distance) does not cancel out, so the molecule is polar, with some charge distribution remaining due to the unequal pulling effect.\n\nIn CF3Cl, the shape is tetrahedral, with the 3 Cl atoms and 1 F atom bonded by single covalent bonds to the central C atom. The bond pairs spread out with the 3 Cl atoms pulling at the bottom and the 1 F atom pulling at the top. The pulling effect of the 2 Cl atoms at the sides cancels out, but that of the F atom at the top and the Cl atom at the bottom does not, as the pullin effect of 2 different atoms is different. Hence, as before, overall dipole does not cancel and the molecule is hence polar.
82092
just to add to what rb42rdsuns said-\n\nCovalent bonds are formed when atoms "share" electrons so that each nucleus "thinks" that it has, typically, 8 electrons in its valence (outer) shell.  This is typically a lower energy system, which is favorable.  When the two atoms are identical (for example, two hydrogens), the electrons are shared equally  between the atoms.  Sometimes one atom attracts the electrons "better" than the other atom, and this results in a polar bond, in which each of the two atoms has a slight charge.
1027607
Covalent bonds are where two (or more) atoms "share" outer layer electrons in order to achieve stability. Polar molecules are where the electronegativity of the atoms do not cancel each other out, and hence the molecule forms a charge.\n\nA carbon and a hydrogen forms a covalent bond. The carbon has 12 protons while the hydrogen has only one. Hence, the carbon will draw the shared electron from hydrogen towards itself more than that of the hydrogen drawing the electron shared by the carbon, and hence the carbon becames negatively charged because the electron from hydrogen spends more of its time around carbon while the hydrogen, left with its single proton, becomes positively charged.\n\nAn example of a polar covalent bond is water. \n- O---H +\n    /\n    H\n   +
837976
A molecule's structure can determine both chemical and physical properties of the compound (or element).  For example, the water molecule is asymmetric along one axis, making the oxygen atom side negative, and the hydrogen atom side positive.  The water molecule is said to be polar, and it will dissolve other polar molecules (and ionic substances) much better than non-polar molecules.  The molecule is also very stable, so water doesn't react chemically very easily - it doesn't burn, for example.
621085
http://www.chemguide.co.uk/atoms/bonding/vdw.html
1008726
Strong Love!\n\nIn other words, it's a covalent bond because sharing of electrons takes place in these elements when they combine with each other.
740473
When a single bond connects two carbon atoms, it sits between the two nuclei. This type of bond is called a sigma bond and free rotation is allowed simply because there is nothing hindering it. When a second bond forms, it cannot form right between the two atoms because the sigma bond is already sitting there. Instead the new bond has to wrap around the sigma bond and the orbitals of the new bond look like the arms of two people with a beach ball between them clasping hands (the beach ball representing the sigma bond). This type of bond is a called a pi bond and, although it is a single bond, the orbitals composing the pi bond overlap in two places, just like two people hugging the same beach ball will touch each other in two places. This locks the relative configurations into place. One arm of the pi bond cannot move without moving the other arm, so the atoms are fixed relative to each other.
950410
Mainly H-bonding (intermolecular forces)
78348
The answer has to do with symmetry of the molecule and hydrogen bonding.  That should get you going in the right direction
840267
The word molecule tells you that it is a covalent compound (if it were ionic, it would be called a unit cell). Covalent compounds are USUALLY between nonmetals but in some cases can be between a metal and a non-metal. It all boils down to electronegativity difference (how much harder one atom is pulling on the electrons in question than the other atom). I hope this helps!
11021
covalent bonds are called the directional bonds.because the orbitals involved in bonding have specific direction where they bond.
361732
Lewis structure of CH2Br2\n\nIts identical to the lewis structure of methane but just replace two hydrogen atoms with bromine atoms (remember to add the three lone pairs around both bromine atoms).\n\nNow about polarity:\n\nThe C-Br bond is then considered to be polar. Having bromine slightly negative and carbon slightly positive. Over all the molecule is polar.\n\nSymmetry:\n\nAnd yes dibromomethane (CH2Br2) has two planes of symmetry, one horizontal and one vertical. In order to verify this, you have to look at the molecule in three dimension and not two dimentional (as drawn on a paper)
912679
PCl3 has the same shape as NH3 (tetrahedral with P in the center, the 3 Cl at the 3 corners and a lone pair at the fourth corner) So the polar covalent bonds don't cancel out each other\n\nSO3 is planar trigonal and thus the dipole moments cancel out each other and it is non-polar\n\nCF4 has a tetrahedral shape and since all bonds are the same they cancel each others dipole moment;the molecule is nonpolar\n\nCH2F2 has the approximately the same shape as CF4, but since not all bonds are the same their angle is a bit different and the sum of the dipole moments is not zero; thus the molecule is polar\n\nSO2 is a bent molecule (because of the sulphur's lone pair), think of it in a way as water with S in the place of O and O in the place of H so it is polar.\n\nCO2 is a linear molecule (O=C=O) so the dipole moments of the two identical polar bonds cancel out each other; the molecule is nonpolar\n\nO=C=S has different polar bonds, so although they have opposite directions the result will be a slight dipole moment, so the molecule is polar.\n\nIn all your questions you have to compare a polar and a nonpolar molecule. Of course the one with the strongest dipole-dipole interactions in each case is the polar molecule.
589096
Polar molecules, such as water molecules, have a weak, partial negative charge at one region of the molecule (the oxygen atom in water) and a partial positive charge elsewhere (the hydrogen atoms in water). \n\nThus when water molecules are close together, their positive and negative regions are attracted to the oppositely-charged regions of nearby molecules. The force of attraction is called a hydrogen bond.
884639
The bonding will indicate both of these. \na) CH3OH - sp3 O - H single bond\nb) CO32- sp2 O-H 1/3 double bond character through resonance\nc) CO2- sp C - sp2 O, double bond\nd) CO - sp C - sp O, triple bond\nThen longest to shortest is: a) b) c) d)\nWeakest to strongest is: a) b) c) d)
126604
Polarity is determined by the difference of elctronegativities. (less than .3) Covalent bonds do not conduct electricity so an element being polar means not a conductor.