Chemistry 101

[Jay-qu]

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. :Waldo:

..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 B)

[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/substance-info/profiles/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. :D

[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?

[Mercedes Benzene]

Hmmm.... how to explain this...

I'll try.

 

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?

 

Okay, if n=3, then it means that there are 3 azimuthal quantum values (l): 0, 1 and 2, as given by the statement 0 <= l < n (l = n-1).

Anyway, l = 1 includes 1 type "s" orbital. l = 2 includes 3 type "P" orbitals. l = 3 includes 5 type "d" orbitals. If you add the total number of orbitals up (1+3+5), you get 9.

 

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?

Hmmm... again, it's rather hard to explain.

 

Basically, there are 4 orbitals that fulfil those requirements (+2/-2) when n = 4. There are m=+2/-2 orbitals in the l = 2 subshell, and m=+2/-2 orbitals in the l= 3 subshell. (4*2) = 8.

 

I hope this helps!

[XrayBravoRomeo]

I have a question regarding hydrogen flouride. The electronegativity difference between them is 1.9, so it should be an ionic compound right?

 

However, my book says that an ionic compound is when a metal, and a non-metal bonds together, and H and F are both non-metals.

 

I also read that HF is an acid, and it has a hydrogen bond. Like ammonia (NH3) and water. But none of them has ionic compound between the atoms? They have polar covalent bonds?

 

Long story short:

What bond is between the atoms in HF?

 

Sorry if this was an obvious question, I just started chemistry :)

 

Thanks in advance

[learnin to learn]

actually it is a pretty good question! and I for one have no clue! :Glasses:

[Jay-qu]

I think it is a covalent bond. It is an acid, moderately strong in water but extremely stong in higher concentrations. It will hydrogen bond also.

[Mercedes Benzene]

Hydrogen Fluoride is indeed an ionic compound. The hydrogen counts as a "metal" do to its +1 charge. Hydrogen needs to lose one electron. Fluorine needs to gain one. They don't care that they're both gasses. :Glasses:

I'll also note that Hydrofluoric acid is considered a weak acid and does not completely dissociate in water. This characteristic may make it seem more like a covalent molecule. :)

[hallenrm]

Chemical bonds are like shades of colour in real life, there are seldom a perfwct white or black, they are shades of gray. Coming back to chemical bonding, it is just a concept to describe the sharing of electrons between the atoms in a molecule; if it is more inequitable, it is termed ionic and if it is equitable it is termed covalent, just like poor and rich or for that matter capitalism and socialism.!

 

:Glasses:

[XrayBravoRomeo]

Thanks for the replies:)

[Michaelangelica]

Being a mad gardener I would really like to understand this. "Caton exchange Capacity"

But I can't

I have NO chemistry.

 

I don't understand all the - and + tives.

 

Can anyone help?

http://syllabus.syr.edu/esf/rdbriggs/for345/cation.htm

[Mercedes Benzene]

By just skimming breifly through the article, it appears they are talking about ions (specifically cations) and their interaction with colloidal suspensions of clay-like materials.

 

First off, an ion is a charged particle. A cation is a positively charged ion.

The + and - they refer to denote the charges of the ion. They set it up very strangely in this article which is probably why you had a hard time comprehending what was going on.

For instance, they mention Al+++. Anywhere else, that would be very poor structuring. In chemistry you would write Al +3, or Al 3+ (with the "+3" as a superscript). This represents an Aluminum cation, that is, an Aluminum atom stripped of 3 electrons. Since electrons have a negative charge, taking away three would leave a positive 3 charge.

 

I hope this helps clear up things a bit. Let me know if you have any more questions, and I'll try to read the article more carefully. :lol: