Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: imd321 on 29/12/2009 19:05:58
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I believe iron, cobalt and nickel are the only magnetic metals. Why is this and is a coincidence that they are next to each other on the periodic table?
[MOD EDIT - PLEASE ENSURE THAT YOU PHRASE YOUR THREAD TITLES AS QUESTIONS, IN LINE WITH THE FORUM POLICY. THANKS. CHRIS]
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Don't know. Magnetism is strange.
My spin on it (http://www.thenakedscientists.com/forum/index.php?topic=25747.msg280414#msg280414)
And the explanation to why some materials is more magnetic seems to have to do with the way their outermost electrons align up their spins? Magnetics (http://www.newton.dep.anl.gov/askasci/phy05/phy05054.htm)
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Maybe you should read 'magnetics' before my 'spin' on it?
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Electrons have spin, a property that gives them a magnetic moment it creates a magnetic field.
The spins of electrons in most atoms are paired up and so their magnetic effects are in effect cancelled out. a bit like having pairs of bar magnets stuck together. Now, iron cobalt and nickel are what is known a "transition elements" this means that the differences between these elements are less than those of the main elements in the periodic table because it is only electrons in lower shells and not the main outer shell that are being added as they increase in atomic number (that is the number pf protons and electrons that they have). The reason for this is complicated and beyond the detail possible in this short note. one feature of this lower shell addition is that there are more unpaired electrons than in most other atoms. This excess of unpaired electrons means that they have stronger residual magnetic moments and can line up "head to tail" like little bar magnets and increase their magnetic field instead of neutralising it and stay there at room temperature. instead of randomising after they have been lined up by placing them in a magnetic field. This makes them ferromagnetic.
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Soulsurfer, is that the reason they are next to each other on the periodic table?
That they are 'transition metals'
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They are "transition metals" because someone decided to call them that, and the name stuck. Their posiition in the periodic table is determined by their electronic structure and that is also responsible for thir magnetism. On the other hand, gadolinium is also magnetic and its neighbours are not. I have heard that plutonium is magnetic too; I havent been able to check.
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yor_on yes
Gadolinium is a rare earth element this is a "super Transition" in which only electrons two shells below the main outer valence shell are being added with increasing atomic number most of the transuranium elements are members of the second super transition.
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Let me add a little bit more about the electronic structures of atoms.
Because of the quantum structure of matter, electrons can only link with an atomic nucleus in certain specific orbitals. Only the lowest energy of these are stable. Each of the orbitals can only hold a precise number of electrons.
The total number that they can hold in order of size are 2 8 18 32 ....
This structure is also broken down into sub groups
2 2,6 (8) 2,6,10 (18) 2,6,10,14 (32)
This is associated with the amount of angular momentum the electron can have.
note these numbers derive from the sequence 1,3,5,7 with each position able to take two electrons of opposite spin.
As atoms increase in atomic number from 1 to about 100 the electrons are added to these orbitals at the lowest energy possible but these are not added precisely in sequence because the 2 and 6 orbitals are much lower energy than the 10 and 14 ones so these are filled first.
This means that the outer shell of any atom never contains more than 8 electrons and it is this outer shell that determines the chemical properties of the atom and there are in effect only eight basic sets of chemical properties that an atom can have!! (that is why chemistry is such an easy subject LOL)
when the lower shells are being filled in the transition elements and rare earths/actinitdes adjacent elements only change very slightly in their chemical properties although unpaired spins differ greatly so their magnetic properties can differ a lot.
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Interesting.
So could i say that certain arrangements of electrons (orbitals) is craved before they can become the most magnetic? If I would look at it as some sort of puzzle :) And that they need to have their spin aligned in the same direction?
And that there are certain other configurations "super Transitional's" that also becomes magnetic although not because their utmost orbital spin?
So can there exist 'strong' magnetic materials that doesn't need it to be the utmost spin to be aligned.
What I'm wondering about is if magnetism only trust in those utmost 'spins' or if it is some sort of 'puzzle' that craves certain configurations, but not locked to those utmost orbitals only?
Hope it's understandable.
Thanks to both of you.
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Sorry I do not understand your question. I appreciate that English is probably not your first language. Could you try to express it again using different words and I will try to answer it.
I will add paramagnetic properties are caused by unpaired spins in electrons and ferromagnetism is an extreme case of paramagnetism where the magnetic alignments are strong enough to allow aligned atoms to lock together at a reasonable temperature. Because of the order in which the electrons fill the orbitals it is possible for transition elements to have several electrons that are unpaired. Most other atoms only have one unpaired spin at most.
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Well, i was wondering if the internal structure could have something to do with magnetic materials too, or if it only is the alignment of spin at the utmost orbitals that creates it. if the internal structure can create it too, sort of?
As all materials seem to be able to become 'magnetic'
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Virtually anything that we commonly think of as matter can be influenced by a magnetic field, provided certain conditions are met. However, for the most part there are only 3 elements (and then compounds made that include those elements) which are commonly thought of as magnetic: Iron, Nickel, and Cobalt.
While most any matter can be influenced by a magnetic field, these 3 elements are thousands of times more susceptible to the effects of a magnetic field. Their interaction is so strong, their effects so dramatic, and other things so weak or subtle, that we generally just think of other things as not "magnetic".
The reason these three metals are so strongly magnetic is not completely understood. Their outer-most electrons tend to possess spins that line-up. This alignment, whatever the reason, is what gives cobalt, iron and nickel their very strong magnetic properties compared to most other materials.
Michael Pierce
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what do YOU mean by "internal structure" of an atom. is it
1 the structure of the lower electron orbitals?
2 the structure of the nucleus itself?
unpaired spins in the lower shells have a significant effect as I have already said. Nuclear effects are very small and create very small energy shifts in electrons but are used to great effect in nuclear magnetic resonance measurements.
As atoms are electromagnetic structures ALL atoms have magnetic properties ferromagnetism and antiferromagnetism are just extreme cases of a very broad spectrum which includes paramagnetism and diamagnetism (QV)
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Don't really know there, in a way this talk about orbitals only seem to describe probabilities? That's why I thought of it as a 'puzzle' and then I started wondering if it only was locked to the spin, and if so, if there were different combinations that could create 'magnetism' in a piece of matter. Involving both spin and the 'placement' of orbitals?
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I looked it up and it seems that there are four 'properties' to the electron, and those need to be different for each ‘orbital’.
N- Which is its intrinsic 'energy'
L- Which is the ‘orbital’ itself as I understand it, its ‘height’ over the nucleus, sort of.
M- Which is the 'direction' of the orbital around the nucleus
Ms- Which is the Spin.
The two most important of these are N and L.
According to the Pauli Exclusion Principle no two electrons may share the same values for all four numbers. And the Pauli Exclusion Principle states that no two fermions (matter) can occupy the same quantum state at once.
The reason that there can be two electrons in the same orbital is their opposite spin that then allows them to be of different quantum states sharing what’s called an orbital. And the orbital represents the region where an electron can be expected to exist with most probably (90 percent probability more or less)
“In the ground state of an atom, the states are "filled" in order of increasing energy. i.e., the first electron goes into the lowest energy state, the second into the next lowest, and so on. The fact that the 3d state is higher in energy than the 4s state but lower than the 4p is the reason for the existence of the transition metals. “
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An electron 'orbiting' will be 'placed' in different orbital due to its energy,
where N1 is the closest to the nucleus. N2 the orbital above etc.
And L is the orbital. The rule here is L=N-1
So if N = 1 then L (orbital) = 0
M is the orientation of the orbitals in XYZ (Three dimensions)
And M can equal anything between -L and +L.
For example If L is 1, then M can equal -1,0,1.
(which then mean that N=2 as L=N-1)
Ms which then is 'Spin'. And the spin of the electron can equal - 1/2 or 1/2.
And so for any two electrons in the same orbital they need an opposite spin.
And yeah, it gives me a headache :) as this too is true.
---Quote----
A true electron orbit is not nearly so simple as a circle or ellipse. According to quantum physics, there is no set motion. We can talk about an average radius of an orbit. We can talk about the angular momentum and energy of an orbit. We can talk about how much of the orbit is in the horizontal plane.
In reality, the electron's orbit is not any specific motion. It bounces all over the place. Higher energy electrons have a greater average radius. Different electrons have different angular momentums. Exact path cannot be determined.
Dr. Ken Mellendorf
Physics Instructor
Illinois Central College
---End of quote---
(Why I use this citation is that all the other 'values' we use to describe that electron with are distinct 'properties' of something we just can describe by probability, if you see how I think here.)
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And when we speak about magnetism we say that “atomic dipole moments are locally aligned, producing a macroscopic, non-zero magnetic field from the domain.”
(Which just means, creating a magnetic field by their ‘dipoles’ being aligned in the same direction, like when you connect magnets to each other.)
And a ‘Dipole’ is a pair of equal and opposite electric charges or magnetic poles, separated by a small distance.
Do spin contain opposite magnetic poles?
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Which then mean that the electron is a charged particle having an angular momentum created by spin (Ms) and orbital motion (L) Or should that be (M)? Or both (L and M)?
“From classical electrodynamics, a rotating electrically charged body creates a magnetic dipole with magnetic poles of equal magnitude but opposite polarity.
This analogy holds as an electron indeed behaves like a tiny bar magnet. One consequence is that an external magnetic field exerts a torque on the electron magnetic moment depending on its orientation with respect to the field.”
So atomic dipole moments are when the electron spin is ‘spinning’/aligned in the same ‘direction’.
And the ‘spin’ that we describe as being aligned comes from the Dirac equation, a fundamental equation connecting the electron's spin with its electromagnetic properties.
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Electron magnetic dipole moment (http://en.wikipedia.org/wiki/Electron_magnetic_dipole_moment)
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I do try to understand this but it is strange.