Chemistry 101

[Barry Scott]

While studying biology and chemistry the words polar molecules keep popping up particularly in bonding, can someone explain to me what they are?
Thankyou

[Mercedes Benzene]

Polar molecules have elemental components that are arranged in a manner that provides a "negative end", and a "positive end".
Water is one such molecule. The hydrogens have a slight positive charge, and the oxygen has a slight negative charge.
This is especially important in biology for multiple reasons. For instance, polar molecules are eoften very good solvents.
You can ask our user HydrogenBond for more info.

[Jay-qu]

Originally Posted by Mercedes Benzene

Polar molecules have elemental components that are arranged in a manner that provides a "negative end", and a "positive end".
Water is one such molecule. The hydrogens have a slight positive charge, and the oxygen has a slight negative charge.
This is especially important in biology for multiple reasons. For instance, polar molecules are eoften very good solvents.
You can ask our user HydrogenBond for more info.

..extending..
Polar bonds arrise from a difference in electronegativity between the bonding atoms. This means that one atom is better at 'pulling' the electrons towards it. In the case of water, it is because the oxygen atom has 8 protons to pull with, while the hydrogen only has 1.. this makes the electron in the hydrogen atom get pulled towards the oxygen and hence making the hydrogen part of the water molecule slightly positive, the oxygen then becomes slightly negative. It is this effect that makes water liquid at such high temperatures and also that when it freezes it expands

[learnin to learn]

what is the difference from a polar molecule and a molecule that is not polar? what characteristics does a polar molecule have that a molecule that does not?

[Mercedes Benzene]

what is the difference from a polar molecule and a molecule that is not polar? what characteristics does a polar molecule have that a molecule that does not?

Really nothing... except for polarity. Polar molecules have atoms with greatly differing electronegativities. That's what makes them different from a non-polar molecule.

[Jay-qu]

well the substance will hence have a higher melting and boiling point..

[hallenrm]

This is especially important in biology for multiple reasons. For instance, polar molecules are eoften very good solvents.

Only for polar solutes like salts!! They are important in biology because most molecules in biological organisms are also polar!!

[Michaelangelica]

What is hexavalent chromium?Please?
What is it used for?
It seems to be the waste product of some manufacturing process What is that?
Thanks

In 2004, the state Department of Health Services confirmed an increased lifetime risk of illness, particularly of lung cancer, for those exposed to airborne particles of hexavalent chromium released during plant operations.
The degree of risk depends on the time and length of exposure; and the age at which a person was exposed.

http://www.willitsnews.com/localnews/ci_4367903

Very small quantities of chromium (III) compounds are essential for your health and well-being. Chromium VI compounds are usually highly toxic

http://www.npi.gov.au/database/subst...ofiles/25.html

[Mercedes Benzene]

What is hexavalent chromium?Please?

Hexavalent simply means that the chromium is in it's +6 (VI) oxidation state in a given compound.
Chromium also exists in 2, 3, and 4 oxidation states.

I'm not sure what chromium +6 is specifically used for, but I do know that chromium and its compounds are used as alloy agents for steel, and they make some pretty colorful compounds! An example would be the vibrant orange Ammonium dichromate.

[dlm]

I was wondering if anyone can help me with these questions.

What is the total number of atomic orbitals possible at n =3?
I thought the answer would be 5 but it's actually 9, can someone explain why there are 9 orbitals?

I'm also having trouble with another question.
It asks: How many electrons in an atom can have the following sets of numbers: n= 4 and m(subscript l)= +2/-2? The answer is 8 while I thought it was 14. Can someone also explain this?