How do you predict that a covalent bond between two atoms is polar?
361166
Look at the electronegativity of both atoms. The electron density is going to be clustered around the more electronegative one. Electronegativity increases as you go up and to the right on the periodic table (noble gases not included), so Fluorine is the most electronegative atom.\n\nSo, the bond between nitrogen and oxygen is polar, but only slightly. The bond between iodine and fluoring is quite polar. The bond between cesium (the least electronegative natural element) and fluorine is so polar, that all the electron density is clustered around the fluorine, making it an ionic bond rather than a covalent bond.
740266
Silver Nitrate is a salt, meaning it's very polar.  But polar/nonpolar is usually used to describe covalent bonds.
847949
Polar.  The stronger the intermolecular forces, the higher the melting point.
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.
976900
Chemical bonds form when electrons are shared, like in covalent bonds.  The atoms in the bond share a certain number of electrons between them usually so they both have a complete octet of electrons.  Another type of bond is ionic.  This is when one atom completely pulls off an electron from the other atom.  This results in a negative charge on the taker and a positive charge on the giver.  The bond is formed by the electromagnetic force acting between these two dissimilar charges.
899426
the way i like to look at is... in a given molecule, you usually have one or two (maybe three) central atoms.  for example, in CH3OH, the carbon is your central atom.  in C2H5Cl, two two carbons are your central atoms.\n\nnow, taking a look at the central atom, see if it is bonded to identical atoms an all sides.  For example, if the carbons are bonded to four idental atoms, then it is non-polar.  if the carbons are bonded to different atoms, then it is polar.\n\nIf you take a look at CH4,  there are dipole moments between the bond  between the carbon and hydrogen, but the molecule as whole is considered non-polar because the carbon is bonded to four identical atoms.  \n\nhope that helps.
525685
You can approach this is one of two ways:\n\n1)  By analogy with H2O (because O and S are both in the same group)\n\n2) From first principles ie octet rule, Lewis diagram, hybridisation, shape. \n\nNow S has 6 electrons in outer shell, while H has 1 each, therefore, S will share 1 e- from each H to complete its octet and each H will share an e- with S so H (which is too small to have 8e-s in outer shell) will have a full outer shell. So S is now covalently bonded to to H atoms, accounting for 4 e-s, with 2 non-bonding pairs. That makes 4 pairs of electrons around S all together, so hybridisation is sp3. Shape is tetrahedral minus two vertices ie bent (just like H2O).\n\nI hope this helps.
335753
1. Covalent Bonds\n2. Ionic Bonds\n3. Hydrogen Bonds
734468
A molecule is said to be polar when the atoms are different in its electronegativity and its magnitude does not cancel off each other. Water itself is made up of Oxygen & Hydrogen atom. The electronegativity of o2 and h2 is the same. Thus, there are no dipole movement in the oxygen-hydrogen bond. However, the magnitude of the 2 hydrogen atom that is attached on the oxygen bond is in a 45 degrees manner. Thus, when the magnitude of the whole molecule is considered, the molecule is deemed to be polar.
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.
837121
Hmmm.. The one affecting the boiling point is the intermolecular force..\nAs you can see, most of the compound here is polar. \n\nTherefore all you have to do is if the compound is consisted only of 2 elements (Group 17), you'll have to calculate the electronegativity difference. The more difference between them, the boiling will increase as well.\n\nIf there is more than 2 atoms in a molecule, you'll have to see the dipole moment magnitude (a.k.a polarity). The higher the magnitude, the higher the boiling point will be.\n\n\npeace\nvixklen
666235
The theory of valency which we have been developing is known as valence bond theory. One further feature of this theory is that it may be used to predict (or in some cases, rationalize) the observed geometries of molecules By the geometry of a molecule we mean the relative arrangement of the nuclei in three-dimensional space. For example, assuming the two O—H bonds in the water molecule to be similar and hence of the same length, the angle formed by the two O—H bonds (the HOH angle could conceivably posess any angle from 180° to some relatively small value. All we demand of our simple theory is that it correctly predict whether the water molecule is linear (bond angle = 180°) or bent (bond angle less than 180°)  Or as another example, it should predict whether the ammonia molecule is planar   or pyramidal \n \nhttp://www.chemistry.mcmaster.ca/esam/Chapter_6/section_4.html.
987785
I think you've got it a little backward.  In molecules like water, there is a permanent imbalance of electron distribution in the molecule.  The oxygen atom in water always has a partial negative charge, and the hydrogens are always partially positively charged.  This is so because the electronegativity of oxygen is very large compared to that of hydrogen.  Therefore, when the two elements form covalent bonds in water, the electrons are pulled more strongly toward the oxygen atom, giving it a negative charge.\n\nBecause of this permanent polarity in the molecule, water molecules are dipoles (molecules with two regions of opposite charge).  When two molecules of water interact, they do so through dipole-dipole interactions.  That is, the positive part of one water molecule interacts with the negative part of a different molecule.\n\nInduced dipole interactions occur between non-polar molecules.  Because of the random movement of electrons in a molecule, just by chance the electron distribution will occasionally be lopsided, giving a slight positive charge to one part of the molecule and a slight negative charge to another part.  If this molecule is close to another non-polar molecule, it's partially charged areas will push the electrons away in an adjacent molecule, inducing a dipole in the second molecule.  \n\nSo, dipole-dipole interactions occur between molecules which are already polar, and induced dipole interactions occur between non-polar molecules, or between polar and non-polar molecules.\n\nCheck out a chemistry book for more details.
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.
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Molecular bonding.\n\nThis is a function of the atomic weight (protons in the nuclei) and the distrobution of the electron shell.  Give me three years and I will explain it fully.
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)
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a polar bond is one which the shared electron, making the bond, is closer to one atom.  A bond between two identical atoms is non-polar because the atoms have the same electronegativity.\n\nElectronegativity is the affinity for an electron.  Fluorine is the most electronegative element and Francium the least.\n\nHydrogen has an electronegativity of 2.2 and fluorine 3.98, prompting the electrons to be closer to fluorine, consequently making the hydrogen partially positive and fluorine slightly negative.