Trying to determine if a molecule is polar or nonpolar

In summary, the molecules with unpaired electrons and double bonds are considered polar, and drawing a Lewis structure for molecules with an odd number of electrons can be done using various resources. In terms of naming compounds, IUPAC establishes conventions for nomenclature and the first principal quantum number primarily determines the energy state of an atom in its ground state. Additional quantum numbers involve angular momentum and interactions with magnetic fields, and can be used to determine the energy of valence electrons in different atoms in their ground states.
  • #1
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1) when trying to determine if a molecule is polar or nonpolar, how do unpaired electrons and double bonds affect it? for example, in CO3 (2-), its trigonal planar but one of the C=O bonds is a double bond...is this polar or nonpolar?

2) what do you do when you have an odd number of electrons and you want to draw the lewis structure?

3) when naming compounds, when do you use the di, tri, tetra prefixes? for example, P205 is diphosphorous pentaoxide, but BaCl2 is not barium dichloride but rather barium chloride only.

4) when talking about quantum numbers, how do you know when an atom is in its ground state? the question i have is regarding a valence electron in a K atom in its ground state and the quantum number choices are (n,l,m,s): (a) 3,0,0,1/2 (b) 3,1,1,1/2 (c) 4,0,0,1/2 (d) 4,1,1,1/2 and (e) 4,2,1,1/2

i thought the first principal quantum number (n) tells the energy state but from there i don't know which to choose.

another example is the quantum number for a valence electron with greatest energy in a P atom in ground state. again, the choices are (a) 2,0,0,1/2 (b) 2,0,1,1/2 (c) 2,1,0,1/2 (d) 3,1,1,1/2 and (e) 3,2,1,1/2

again, doesn't the first number tell us about the energy? so I am assuming the 2nd problem (P atom) is between d and e but from there i don't know which one.

thanks.
 
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  • #2
1) With regard to molecular geometry - http://www.up.ac.za/academic/chem/mol_geom/mol_geometry.htm [Broken]
http://www.chem.uncc.edu/faculty/murphy/1251/slides/C19a/

2) Try these with respect to the Lewis structure.

http://en.wikipedia.org/wiki/Lewis_Structure
http://www.chemtutor.com/compoun.htm#lewis
http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/lewis.html#c1

3) With regard to naming compounds, International Union of Pure and Applied Chemistry (IUPAC) establishes conventions for nomenclature.

I think P2O5 is also called phosphorus pentaoxide, and there is also P2O3 or phosphorus trioxide (or phosphorus (III) oxide). I would think most introductory chemistry textbooks would have an explanation of the nomenclature.

4) K is an akali metal, so has 1 s electron in the valence shell. K begins Period number: 4. The s electron can only have l = 0 and therefore m=0, and that leave 1/2 for the electron spin.

Phosphorus is in group 3.

Here is a nice general reference on the periodic table - http://www.webelements.com/ .

http://hyperphysics.phy-astr.gsu.edu/hbase/atpro.html

All the quantum numbers have something to do with energy, but the biggest factor is the principal quantum number, while the others involve the angular momentum, and interactions with magnetic fields.

http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/hydrad.html#c3

http://hyperphysics.phy-astr.gsu.edu/hbase/qunoh.html#c2

http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/qnenergy.html#c1

http://hyperphysics.phy-astr.gsu.edu/hbase/atomic/atstruct.html#c1
 
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  • #3


1) Unpaired electrons and double bonds can affect the polarity of a molecule. In general, molecules with polar bonds (such as C=O) will be polar if the polar bonds are not evenly distributed throughout the molecule. In the case of CO3(2-), the molecule is trigonal planar and the C=O bonds are evenly distributed around the central carbon atom. This results in the overall molecule being nonpolar.

2) When drawing the Lewis structure for a molecule with an odd number of electrons, you should first determine the total number of valence electrons and then place them in the structure around the atoms. If there are any leftover electrons, they should be placed on the central atom.

3) The prefixes di-, tri-, tetra- are used in compound names to indicate the number of a certain element present in the molecule. In the case of P2O5, there are two phosphorus atoms, so the prefix di- is used. In BaCl2, there is only one barium atom and two chlorine atoms, so the prefix is not necessary.

4) The first principal quantum number (n) does indicate the energy level of an electron, but it does not tell us which specific energy level an electron is in. In the case of a valence electron in a K atom in its ground state, the correct quantum numbers would be (a) 3,0,0,1/2. The energy level is n=3, the orbital shape is s (l=0), the orientation is not specified (m=0), and the spin is +1/2 (s=1/2).

For the P atom, the correct quantum numbers for a valence electron with the greatest energy in its ground state would be (e) 3,2,1,1/2. The energy level is n=3, the orbital shape is d (l=2), the orientation is not specified (m=1), and the spin is +1/2 (s=1/2).
 

1. What is the difference between a polar and nonpolar molecule?

A polar molecule is one that has a separation of electric charge, with one end being more positively charged and the other being more negatively charged. A nonpolar molecule has an even distribution of electric charge, with no separation of positive and negative ends.

2. How can you determine if a molecule is polar or nonpolar?

One way to determine if a molecule is polar or nonpolar is to examine its molecular geometry. If the molecule has a symmetrical shape, it is likely nonpolar. If the molecule has an asymmetrical shape, it is likely polar. Another way is to look at the electronegativity difference between the atoms in the molecule. If there is a large difference, the molecule is likely polar.

3. What is the role of electronegativity in determining polarity?

Electronegativity is a measure of an atom's ability to attract electrons towards itself in a chemical bond. In a polar covalent bond, the atom with the higher electronegativity will have a stronger pull on the shared electrons, resulting in a separation of charge and a polar molecule. In a nonpolar covalent bond, the electronegativity difference between the atoms is minimal, resulting in an even distribution of charge and a nonpolar molecule.

4. Can a molecule be partially polar?

Yes, a molecule can have both polar and nonpolar regions, making it partially polar. This can occur when there is an uneven distribution of charge within the molecule, resulting in both polar and nonpolar bonds. This is known as a polarizability effect.

5. How does polarity affect a molecule's physical properties?

Polarity can affect a molecule's physical properties in various ways. Polar molecules tend to have higher melting and boiling points than nonpolar molecules due to the stronger intermolecular forces between polar molecules. They also tend to be more soluble in polar solvents, while nonpolar molecules are more soluble in nonpolar solvents. Additionally, polarity can impact a molecule's reactivity and ability to form hydrogen bonds.

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