Why is HClO4 stronger than HClO?

Hi,
so this monday we had chemistry class again and because we are learning about halogens our teacher mentioned some acids and she explained why some of them are stronger than other. She got to the point of comparing HClO4, HClO3, HClO2 and HClO. She arranged them in this order in decreasing acidicity explaining why. As I found out over time, she is oversimplifying things, in this post I will try to show why they are in this order.

Perchloric acid 60 percent.jpg

Almost like water, the picture of perchloric acid. (HClO4)


So here we have four acids (to make it faster I will compare only first and last one). Both are same except that there are three more oxygens in HClO4 and the oxidation number of Cl is VII on the left and I on the right. Now this has to be the reason for different properties.

In all of those molecules Cl is the middle one, which means that all oxygens are connected to it with double bond, except one with only simple one which has hydrogen on the other side.

The picture shows the structure of these molecules.

So as you probably know water has what is called “dipole moment”. This is a term that is used for molecules that have partiall charge on one side and the other charge on the other side.

This has very interesting properties but what is important is that HClO4 has this too, and much more than HClO because there are oxygen ions which have charge of -II making chlorine in the middle of them a lot “ripped off” because there are those oxygens with higher electronegativity that are trying to get those electrons to get on the configuration of noble gases.

Now before the conclusion we must clear out the definition of acidic molecule. Such a molecule is acid when it is good at giving H+, so now the question is, why is HClO4 better in giving H+ than HClO?

So the key lies in what happens when these acids break up. When HClO4 becomes ClO4- there is not so much stress into getting the hydrogen back because delocalized electrons from the other oxygens [1] can ease it up making the molecule more stable while in HClO loses only one of two donors of oxygen making the molecule want it back a LOT.

Simply:

Electron withdrawal increases strength.

If you are not sure about this, ask me in the comments or check out the resources that I used.

Dragallur

Resources: 1|2|3|4|5|6

[1] Yes oxygens here have all two free electron pairs which are doing some wonders!

 

 

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How does atom looks like?

Hi,
this was a question that friend of mine asked me on one contest I was this weekend. I was sure with the answer but after I said it I was not able to come up with the reason for it, at least I was not sure enough to say something clear.


So what exactly needs to happen for you to see it? There must be a photon which is reflected off the surface. How does this look like anyway on the atomic level? Well the light hits some electron in its way. There is lot of free space so this is why things that are not transparent can be if they are thin enough. The electron absorbs the photon, jumps to higher level (excitation), then it emits photon. Now on what you see depends upon its wavelength. So different materials will like to absorb different wavelengths making the object to have color. You can only change in what orbital you will have the electron so I guess that this is the fundamental difference between various colors of objects (though I did not check it).

So when electron emits the photon you simply do not know what the electron looked like. The only thing that you can get is just photon of some wavelength and there simply is not any way to look on some kind of surface of electron. Another factor is that the light has too big wavelength and you can not observe surface with that because the photon kind of just flows around and when you get to wavelength of the size of atom or smaller, the energy of the photon is so huge that the electron is anyway blown away.

There is nucleus too of course and normally photons do not get there because of this electron cloud around and nucleus is tiny. Otherwise from what I found it seems that again the proton and nucleus as whole is way too small and you can not actually map the surface.


 

But I was talking only about electrons and nucleus. You can actually see atom as whole. Not by microscope because visible light is way to huge. There is what is called Abbé difraction limit so you have to look for atoms in different way, using for example electrons (electron microscopes[1]) and then recreate the image using some cool physics, this is for example picture of silicon carbide:

And the one below is picture made by IBM of individual atoms that are shaped like the letters of IBM.

So while you can not see the atom, you can observe, not electron though or even the nucleus at least in ordinary way. You can for example measure energy or calculate the shape but you can not see them as physical objects.

Dragallur

[1]Electron microscopes observe how electrons bounce of the surface just like photons.

Read more: 1) 2) 3)

pearshaped-2WEB.jpg

The shape of Radium-224 nucleus

 

Higgs boson for dummies!

Hi,
finally here it comes, here it goes, post about Higgs boson is coming. Lets look what the “god’s particle” is how physicists found it and what it means.


 

God’s particle

Lets see how Higgs boson was named the god’s particle.

One of the best particle physicists Leon Lederman who found out that there are more types of neutrinos and so on and on. He wrote a book named the “God’s particle”. The book was partially named like this because the publisher did not want it to be named “Damned particle”.

He did this and now all physicists can agree on one thing, they hate this phrase because Higgs boson has nothing to do with God.

While all journalists can agree that “God’s particle” is amazing phrase.

So if you want some physicist to be angry on you, just mention the God particle and he will never forget.

Higgs boson was found 4.7.2012 in Large Hadron Collider.


Higgs field

What is actually more important than Higgs boson, the particle, is the field from which it came, this is the Higgs field. I already talked in last post about fields and how specific vibrations can form particles. Higgs field can do this too and it makes the higgs boson which decay almost immediately and is really hard to detect.

Higgs field is a very different from other fields because other fields can get to 0 energy while Higgs field can not. What is more accurate to say is that non zero value of Higgs field is less energetic than zero so Higgs field does not want to fall on the value of 0.


What does it do?

Well you may have heard about Higgs field giving mass to matter. This is partially true since when particle interacts with Higgs field they are kind of slowed so they do not travel at the speed of light. Some particles interact more than others like some people interact with group of people more than others because they are well known [1].

At one post I wrote about symmetries, check it out if you did not already. There is symmetry in particles. They are all the same.
What? Now this symmetry is broken, this means that there are differences between particles, thanks Higgs field! This is the most important effect of the field with the effect that while it would not change much the mass of protons and neutrons, it would change the mass of electron rapidly if it would not exist. Now the space occupied by particles as electrons is set and such a light particles need to have a lot of space around them. If you would turn off Higgs field completely, things would probably gone exploding a lot since the size of atom would increase as the space around electron needed would get bigger.

Dragallur

[1] This does not mean that all the mass is from Higgs field, most mass of neutron and proton is made up of energy m=E/c^2.

Picture

 

 

 

The Standard Model for dummies!

Hi,
last time I talked about some stuff like dark matter (1 & 2), dark energy and I did not explain a lot of things which I mentioned and this time I will talk about Standard Model.


Standard model or Standard model of particles and interaction is the model of all observed and proved particles.

The next picture shows how it looks like, you could say that it is the “modern” periodic table or some kind of holy grail of physics.

So in this standard model you have particles that make up everything we know [1].

There are four main groups which are sorted by the forces they interact with.

All of those particles interact with gravity. Quarks also interact through strong nuclear force while leptons do not interact that way, also all of them have whole numbers for charge.

The red part has inside particles which are what is called “force carriers” they carry the fundamental forces with graviton excluded because he is not proven yet.

The most mysterious is the yellow part with only Higgs boson inside, I will make sure to make a whole chapter only about it.

Quarks

Already months and months ago I made post about quarks. Here I will cut it short so, quarks are particles that made everything there is except just a little part which is made from electrons. Quarks normally group together into hadrons – protons, neutrons, pions. Quarks have charge of either +2/3 or -1/3. They also have a property called color which is not color at all and they must group together so their colors cancel into white (white) [2].

Leptons

There are three main particles called: electrons, muons and tauons. Only electrons are actually somewhere while we can create other in the particle accelerator.

All of those have -1 charge but there are other particles called neutrinos. Electrons, muons and tauons all have their neutrino.

I already wrote about neutrinos but they are actually extremely light particles sometimes called “ghost” particles because they can easily go through whole planet Earth without touching anything. They are also electrically neutral.

Force carriers

Gluons are particles that are mass less and they carry the strong nuclear force.
Photons are also mass less and they carry electromagnetism.
Gauge bosons (W+- and Z) carry weak nuclear force.

Most of those particles have mass and that is because of Higgs boson, but that is whole new story which I will have to start with symmetries and fields, stay tuned.

Also main difference between force carriers and everything else is that they do not need any space to exist, there can be millions of them at one spot while only one lepton or quark.

Dragallur


 

[1] I do not talk about dark matter which I mentioned in earlier posts. WIMPs are not here since they do not belong into standard model, those are particles beyond the model even if they exist.

[2] Quarks have 3 basic colors: Red, Green and Blue but there are of course anti quarks which have just opposite colors: Antired, Antigreen and antiblue.