chemistry help?

Question

how can you tell if a bond is polar or nonpolar and how can you tell if a kind of molecule is polar or nonpolar. how do you determine the spape of the molecule( linear, bent, pyramidal, tetrahedral) can you explain how you know if an electron-dot formula is correct? I sort of know how to do this, but just not to sure.
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:Cl:Cl: is this correct?
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O::O is this correct?

Answer 1

You are asking all the essential questions of a chemical bonding unit. I would recommend a thorough reading (or re-reading) of that chapter in your book because it will be very difficult to learn (of for us to explain) how to determine shapes of molecules in this format.

However, bond polarity is easier....A bond is polar if the electronegativity difference between the two bonded atoms is about 0.5 to 1.7. So look up each electronegativity value and subtract the small one from the big one (so you get a positive number). If the answer is between 0.5 and 1.7, it's polar, simple as that!

Whether the whole molecule is polar depends on it's shape (VSEPR shape). Once you learn the shapes and can visualize them, think of a tug of war match between all the atoms. Atoms with high electronegativity values attract electrons more strongly (they win the tug of war). However, due to the shape of the molecule, other atoms may be pulling against each other thus canceling out the attraction of electrons toward any one atom. If the atoms are NOT pulling with equal strength in opposing directions, then the molecule WILL be polar. This is hard to explain without demonstrations and/or graphics. If you kind of understand what I'm typing, you should give your textbook a try, the illustrations may help clarify. Good luck.

You should check EVERY electron dot formula by answering the following: Does my diagram use ALL of the valence electrons? Is every atom surrounded by 8 electrons? Do the hydrogens only have 2 electrons around them? The answer to all 3 of these must be YES if the structure is correct.

Answer 2

Polarity is determined by the difference in electronegativity between the 2 sharing atoms.

EN difference of 0.5 or less is no polar
EN difference of 0.5 -1.7 is polar covalent.

Above that is ionic bonding.

the shape is based on the VESPR formula. If there are no unshared electrons, it will be symmetrical, for example, a tetrahedron for CH4. If there are unshared electrons, it will have a distortion, such as trigonal pyramidal for NH3.

Answer 3

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