why do silicon have a higher melting poing than aluminium?
963128
In general, if the attractive forces between the particles is high, more energy is needed to overcome these forces and the melting point is high. Aluminium has a metallic structure, but silicon has a giant covalent lattice structure, like diamond. the melting point of silicon is higher because the bonding within its structure is very strong (stronger than that of aluminium), and so is harder to break.
192645
I learned that Silicon and Gallium Arsenide are both compounded semiconductors because they each have been doped with elements that make the semiconductor either have electrons as the majority carriers or holes, in either case.  An elemental semiconductor would be carbon, since in its pure elemental state it is a resistor and has neither surplus holes or electrons--it is a semiconductor naturally.
266343
Aluminium or aluminum is the chemical element in the periodic table that has the symbol Al and atomic number 13. It is a silvery and ductile member of the poor metal group of chemical elements. Aluminium is found primarily as the ore bauxite and is remarkable for its resistance to corrosion (due to the phenomenon of passivation) and its light weight. Aluminium is used in many industries to make millions of different products and is very important to the world economy. Structural components made from aluminium and its alloys are vital to the aerospace industry and very important in other areas of transportation and building in which light weight, durability, and strength are needed.\n\nAluminium is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. Aluminium is nontoxic (as the metal), non-magnetic, and non-sparking. Pure aluminium has a tensile strength of about 49 megapascals (MPa) and 400 MPa if it is formed into an alloy. Aluminium is about one-third as dense as steel or copper; is malleable, ductile, and easily machined and cast; and has excellent corrosion resistance and durability due to the protective oxide layer. Aluminium mirror finish has the highest reflectance of any metal in the 200-400 nm (UV) , and the 3000-10000 nm (far IR) regions, while in the 400-700 nm visible range it is slightly outdone by silver, and in the 700-3000 (near IR) by silver, gold and copper. It is the second most malleable metal (after gold) and the sixth most ductile. Aluminium is a good heat conductor which is why it is used to make saucepans.
311707
You may be thinking of silicon doping. That is what they call it when very small amounts of very specific impurities are added to very pure silicon to make semiconductors, like diodes and transistors.
1069552
Solar power is a tricky field to understand....you need to understand p-n junctions, a brief introduction and explanation is here:\nhttp://www.pbs.org/transistor/science/events/pnjunc.html\n\nHere is a brief explanation...this stuff is everywhere on the web and in journals and books if you want specifics.\n\nUsing Silicon as an example which is the most common (this is a bit demonstrative and not completely realistic but should explain some stuff).\n\nTwo silicon wafers are made that are ultra pure and containing small amounts of impurities that are added in a controlled manner.  One wafer has impurities that are n-type, that is when they are in the silicon crystal they have three bonds (compared to the silicons 4) and a dangling lone pair of electrons (nitrogen and phosphorus based are quite common).  This silicon is considered to have electron rich impurities.\n   The p-type impurities in the other wafer are three-bonded as but do not have the lone pair (boron is common).  This silicon has electron poor impurities.\n\nWhen the two wafers are put into perfect contact (in practice the impurities are doped into a single crystal when it is made), electrons from the n-side transfer to the p-side.  This only happens a little bit...at first it is easy to do but as more and more electrons leave an electric field is formed in each half of the silicon that gets greater and greater as the electrons occur.  This field opposes further electron jumping and eventually this stops....an equilibrium situation occurs where both halfs of the silicon have transferred their electrons and charge stops moving.  Note this only occurs at the interface of the two wafers.\n\nBut when the silicon is hit by light, the transferred charges become mobile.  Charge transfer occurs by, (using the p-wafer as an example) an electron transferred to the p-side becoming mobile and moving far away from the interface to the back of the wafer where it is collected by a wire to transfer current to a device...the retun path of the circuit is through the n-side.\n\nI dont' do the process justice...the introduction in this link does a much better job...\nhttp://etd.caltech.edu/etd/available/etd-08062002-192958/unrestricted/Chapter1.pdf#search='semiconductor%20band%20bending%20solar%20power'
590034
Aluminium is very popular for its low weight properties. Thats why they use it in aviation and many other industries.
982255
no, because even silicon which is a semi-conductor and used in microchips when it is purified to 99.999% purity, is only a semi-conductor. silicon occurs in crystal form as silicon dioxide.\nin its different forms it can either be a semi-conductor or an insulator.\nsand isn't going to conduct electricity just because an element appears in it in the form of a compund bonded molecule. afterall, H20 conducts electicity, does sugar that also contains water do so in crystalline form? no!\n\nwet sand will conduct electicity, but that is actually the water doing the conducting of the electrical current.\ndry sand is an insulator just like any crystal.\n\nnow if you happen to walk into an environment that has sand made of 99.999% Si and a thunderstorm blows up, the lightning should scare you a little bit.\n\ncement is made of sand, do you see it conducting electricity?\n\nif you take dionized water, which doesn't conduct electicity well, and dump a little sand into it, it may add enough electolytes to improve he electical conductivity of the water, but dry sand on its own does not!
570003
about the two are mentioned, both are found in the body, but the excess is dangerous with less amount of magnesium than aluminum. have you mentioned other?
575608
Melt the whole mixture and do an electrolysis. Would be quite expensive a process, but might be the only possibility e. g. on the moon in order to produce oxigen. Melting heat might come from sun and electricity from solar panels.\n\nI understood in principle such a reaction is done to make aluminium from bauxite. But in this case the producers immediately use up the oxigen through burning carbon electrodes in order to win the melting heat.
12366
Hi again,\n\n    Well you see, as you know electrons are added up in the 3d orbital in galium, right? So with the increase in number of electrons, the no of protons i.e atomic number also increases. So now the outermost p electron in Al is attracted by 13 protons. But that in galuim is attracted by 31 electrons. So the force of attraction is much more. Now in other atoms, these outer electron attraction is balanced by counter electron electron repulsion. But the added d electrons  cannot shield the outer p electrons much from the force of attraction of the highly charged nucleus. This is similar to the reason why the transition elements contract on increase in at no. Other examples are lanthanide and actinide contractions. If you still dont get it,\nmeet me on Yahoo Messenger. My id is jchemisch. I will talk to you about it. All the best. Hope i can help you if you need!!
729392
There is a strong ionic bond between Ag+ and I- ions thanks to electrostatic attraction. This attractions makes the solid very solid (sable). That is why the melting point is rather high.\nThe attraction between the molecules of vanillin is much weaker, so this molecules can be separated by melting much easier. (This has been called quadrupole or octupole attraction, better known as vanderwaals force (cohesion)).\n\nTh
992740
Higher the charge greater the tendency to accept electrons, hence more acidic\n\nLower the radius, higher concentration of charge, hence more acidic.\n\nIn3+ is larger than Al3+ hence a weaker acid.
1177070
metal is ductile because is is made of the metallic bond, where the large cation is surrounded by the electrons. the electrons will be mobile once it is molten. thus, its unique bond structure made it possible to bent, shape, with malleable property. ceramic is brittle because it's a covalently bonded structure. in covalent bond, it's not as hard and durable as metallic bond. (think about SF6, sulfur hexafluride)
529427
No, copper is NOT cheap, it costs quite a bit more than aluminum pound for pound. Copper has a much lower resistance to electricity than aluminum does. When subjected to the loads household wiring have to deal with, aluminum wiring would have to be prohibitively thick to prevent overheating. Copper provides the best conductivity with the best compactness for the best price.
751854
It does completely. High melting points arise when the atoms of a substance interact and form strong inter-molecular bonds. These are weaker than ionic bonds and covalent bonds but work on the same principle. If the distance between the two atoms is great, the bond strength is low and vice versa. Thus, since potassium has a larger atomic radius, the inter-molecular bonds are weak and it is easier to melt a sample of potassium.
502981
SILICON AND GERMANIUM ARE THE SEMICONDUCTOR MATERIALS WHICH  ARE USED IN THE MANUFACTURE OF THE DIODES AND OTHER ELECTRONIC  COMPONENTS. GERMANIUM COMES FIRST IN THE PERIODIC TABLE WHILE SILICON COMES NEXT.  GERMANIUM HAS LOW CUTOFF POINT THAN SILICON.
305467
It has to do with the amoungt of silica (SiO2) present in the magma.  Andesitic magma is very viscous, and very explosive, which is a function of the amount of silica.  The greater the percentage of silica, the more viscous the magma is.  With higher levels of silica present, and always high amounts of hydrogen, the possibility to create water under extreme conditions (eruption) has a greater potential with the Andesitic magma because of the greater supply of silica.  The greater supply of silica is linked to subduction zones because a large part of the melt is continental crust which is much higher in silica than oceanic crust.\n\nSo, the concentration of water is low in Basaltic Magma because the concentration of silica is also low.  That is also why Basaltic Lava flows instead of exploding.