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Author Topic: What makes a metal a metal?  (Read 9410 times)

imd321

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What makes a metal a metal?
« on: 08/06/2010 08:47:00 »
I understand that metals have a series of properties - sonorous, conduct heat & electricity etc etc.  But do the properties of the element define it as a metal or is there something about the structure of the element that makes it metal and have these properties.  So if an imaginary new element was found, could you tell just from the structure of the atom whether it was going to be classified as a metal or would you need to look at its properties first.


graham.d

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What makes a metal a metal?
« Reply #1 on: 08/06/2010 10:32:57 »
Take a look at these sites:

http://www.chemguide.co.uk/atoms/structures/metals.html
http://www.chemguide.co.uk/atoms/bonding/metallic.html#top

Generally it would be possible to tell if a "new" element was likely to behave like a metal but it would depend on what you know about its atomic composition. The periodic table shows distinct groupings:
http://en.wikipedia.org/wiki/Periodic_table_(metals_and_non-metals)

Soul Surfer

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What makes a metal a metal?
« Reply #2 on: 08/06/2010 11:04:31 »
When in the solid state metals have a crystalline structure that does not restrict electron movement to the immediate vicinity of the atom at room temperature.  That is electrons can move freely through the structure.  This means that the outer electrons are relatively losely bound to the atoms.

Let me explain in a little more detail.  Electrons are fermions and as such only two fermions of opposite spins may reside in any one quantum state (Pauli exclusion principle   PEP) now this is OK as long as atoms are well separated from each other and individual atoms are essentially identical, but as atoms get closer together and form liquids or solids the quantum states start to be effected by each other and to comply with the PEP the quantum states become slightly separated at different energy levels according to the crystal structure and proximity of the atoms so some of the outer electrons of the atoms are at slightly higher energy levels  now the energy level at which the electrons are bound to the individual atoms is called the Fermi level and it may be that some of the higher level energy states of the electrons are above this level and can therefore move through the crystal lattice.  This gives the substance the property of being a metal.  Non metals have strongly bound electrons. 

More interesting are the semiconductors where the fermi level is very close to the top energy level of the electrons and the properties can be radically changed with small quantities of impurities and electric fields.




syhprum

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What makes a metal a metal?
« Reply #3 on: 08/06/2010 19:50:38 »
Why do astronomers refer to all elements other than Hydrogen and Helium as metals ?

Soul Surfer

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What makes a metal a metal?
« Reply #4 on: 08/06/2010 20:50:18 »
It is just a perverse sort of tradition.  They are referring to generically elements that did not form part of the big bang (although it did make a tiny bit of lithium) but were formed in the nuclear syntheses processes in stars that have formed evolved and distributed themselves (by explosion and "evaporation") at the end of their lives which only started quite some time after the big bang had cooled off a bit.  most of these more complex elements are in fact metals.

 

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