I"m looking at the melting temperature of metallic facets, and also notification that the steels with high melting temperature are all grouped in some lower-left edge of the $mathrmd$-block. If I take for example the routine table with physical state suggested at $pu2165 K$:

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I view that (acomponent from boron and carbon) the only facets still solid at that temperature create a rather well-identified block roughly tungsten (which melts at $pu3695 K$). So what makes this team of metals melt at such high temperature?


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edited Dec 24 "19 at 6:59
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Mathew Mahindaratne
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asked Apr 28 "12 at 14:23
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Some determinants were hinted, yet let me put them in an order of prominence and also point out some more:

steels primarily have actually a high melting allude, because metallic interatomic bonding by delocalized electrons ($ceLi$ having just a couple of electrons for this "electron sea") in between core atoms is pretty reliable in those pure element solids compared to alternate bonding kinds (ionic $pu6-20 eV/atom$ bond power, covalent 1-7, metallic 1-5, van-der-Waals a lot lower). Also, ionic lattices like $ceNaCl$ have a greater lattice and also bonding energy, they have actually weak interatomic long-variety bonding, unfavor the majority of metals. They break acomponent or are quickly solvable, steels are malleable but don"t break, the electron sea is the reason for their welding ability.

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the crystal framework and mass play an inferior duty among your filtered elements (just look up the crystal structure of those elements), as metallic bonding is not directional unlike covalent bonding (orbital symmetry). Metals frequently have actually half filled $mathrms$ and also $mathrmp$ bands (stronger delocalized than $mathrmd$ and $mathrmf$) at the Fermi-edge (interpretation high conductivity) and also therefore many delocalised electrons which have the right to move into unlived in power states yielding the best electron sea through fifty percent or less fill bands.

noble metals prefer $ceAu,Ag$ have actually a complete $mathrmd$ orbital, therefore low reactivity/electronegativity and are often supplied as contact products (high conductivity because of "very fluid" electron sea consisting only of $mathrms$-orbital electrons. Unfavor tungsten via fifty percent or much less inhabited $mathrmd$-orbitals they show no interatomic $mathrmd-d$ bonding by delocalized $mathrmd$-electrons, and even more importantly, a fifty percent filled $mathrmd$-orbital contributes 5 electrons to the power band also, while a $mathrms$ just 1, $mathrmp$ only 3, the electron sea is bigger among the $mathrmd$-team.

The "packaging" of core atoms in the lattice (interatomic distance) among the high $Z$ atoms (compared to e.g. $ceLi$) is denser (even more protons, more powerful attractivity of shell electrons, smaller sized interatomic radius), implies more powerful interatomic bonding transmitted by the electron sea:

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You can view here that in each series ($ceLi, Na, K$) the melting points climb to a maximum and also then decrease via increasing atomic number (doing not have unpopulated power claims for delocalized $mathrmd$-electrons), bigger electron sea being here a more powerful aspect than a little bit even more thick packaging.

Boron as a semi-metal mirrors metallic and covalent bonding, Carbon solid directional covalent bonding and also is able to develop a netoccupational of bonds unchoose other non-steel facets reflecting covalent intramolecular bonding, e.g., in diatomic molecules however not solid intermolecular bonding in macromolecules bereason of lacking unpaired electrons.

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So tright here are some bigger patterns for melting points explaining the high melting points of $mathrmd$-metals, but also some minor exceptions to the dominion prefer $ceMn$.