METALLIC METALLIC BONDBONDMetals tend to have high melting points and Metals tend to have high melting points and boiling points suggesting strong bonds boiling points suggesting strong bonds between the atoms. between the atoms.

Even a metal like sodium (melting point Even a metal like sodium (melting point 97.8°C) melts at a considerably higher 97.8°C) melts at a considerably higher temperature than the element (neon) which temperature than the element (neon) which precedes it in the Periodic Table.precedes it in the Periodic Table.

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Happens b/ atoms w/ low Happens b/ atoms w/ low electronegativities.electronegativities.

Metals haveMetals have

1)1)Low I.E.Low I.E.

2)2)Many unfilled orbitals in shells, making the Many unfilled orbitals in shells, making the valence electrons delocalized(shared by) valence electrons delocalized(shared by) amongst all the atoms and they are free to amongst all the atoms and they are free to move throughout the metal.move throughout the metal.

METALLIC METALLIC BONDBOND

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METALLIC BONDMETALLIC BONDMobile sea of valence electrons

Lat

tice

of

po

siti

ve i

on

s

Mobile sea of valence electrons

The attraction is b/ the ions and mobile electrons.

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Metallic bonding in sodiumMetallic bonding in sodiumThe electrons can move The electrons can move freely freely between the between the positively charged ionspositively charged ions, , and so each electron and so each electron becomes detached from becomes detached from its parent atom. its parent atom. The electrons are said The electrons are said to be to be delocaliseddelocalised.. The metal is held The metal is held together by the strong together by the strong forces of attraction forces of attraction between the positive between the positive metal ionsmetal ions and the and the delocalised electrons.delocalised electrons.

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Metallic bonding in sodiumMetallic bonding in sodiumThis is sometimes described as "This is sometimes described as "an an array of positive ions in a sea of array of positive ions in a sea of electronselectrons".".If you are going to use this view, If you are going to use this view, beware! beware! Is a metal made up of Is a metal made up of atoms or ionsatoms or ions? ? It is made of It is made of atoms.atoms.Each positive centre in the diagram Each positive centre in the diagram represents all the rest of the atom represents all the rest of the atom apart from the outer electron, apart from the outer electron, but but that electron hasn't been lostthat electron hasn't been lost - it - it may no longer have an attachment may no longer have an attachment to a particular atom, but it's still to a particular atom, but it's still there in the structure. Sodium metal there in the structure. Sodium metal is therefore written as is therefore written as NaNa,, not not NaNa++ or or potassium metal is written as K but potassium metal is written as K but not Knot K++..

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The metallic bond in molten The metallic bond in molten metalsmetals

In a molten metal, the metallic bond is In a molten metal, the metallic bond is still presentstill present, although the ordered , although the ordered structure has been broken down. structure has been broken down.

On melting, the bond is On melting, the bond is loosenedloosened, , not not broken.broken.

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The physical properties of metalsThe physical properties of metals

Melting points and boiling pointsMelting points and boiling pointsMetals tend to have Metals tend to have high melting and boiling points high melting and boiling points because of the strength of the metallic bond. because of the strength of the metallic bond.

Group 1 metals like sodium and potassium have Group 1 metals like sodium and potassium have relatively low melting and boiling points mainly because relatively low melting and boiling points mainly because

each atom only has one electron to contribute to the each atom only has one electron to contribute to the bond.bond.

They have relatively large atoms (meaning that the They have relatively large atoms (meaning that the nuclei are some distance from the delocalised nuclei are some distance from the delocalised electrons) which also weakens the bond.electrons) which also weakens the bond.

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The physical properties of metalsThe physical properties of metals

Heat and eHeat and electrical conductivitylectrical conductivityMetals conduct Metals conduct heat and heat and electricity. electricity. The The delocalised electrons are free to movedelocalised electrons are free to move and through the motion of the and through the motion of the delocalized electrons, electricity is delocalized electrons, electricity is produced.produced.Liquid metals also conduct electricityLiquid metals also conduct electricity, , showing that although the metal atoms showing that although the metal atoms may be free to move, the delocalisation may be free to move, the delocalisation remains in force until the metal boils.remains in force until the metal boils.

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Electrical conductivity of metalsElectrical conductivity of metals

Animation Animation showing showing electrons electrons moving moving randomly and randomly and then the then the movement of movement of electrons electrons through a wire through a wire

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Thermal conductivityThermal conductivity

Metals are good conductors of heat. Metals are good conductors of heat.

Heat energy is picked up by the Heat energy is picked up by the electrons as additional kinetic energy electrons as additional kinetic energy (it makes them move faster). (it makes them move faster).

The energy is transferred throughout The energy is transferred throughout the rest of the metal by the moving the rest of the metal by the moving electrons.electrons.

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Thermal conductivity of metalsThermal conductivity of metals Metals are good conductors of heat. There are two reasons for this:

the close packing of the metal ions in the lattice the delocalised electrons can carry kinetic energy through the lattice

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Strength and workabilityStrength and workability Malleability and ductilityMalleability and ductilityMetals are described as Metals are described as malleablemalleable (can be beaten into sheets) and (can be beaten into sheets) and ductileductile (can be pulled out into wires). (can be pulled out into wires). This is because of the ability of the This is because of the ability of the atoms to roll over each atoms to roll over each other other into new positions into new positions without breaking the metallic bondwithout breaking the metallic bond..

If another metal is mixed, it’s not easy for the atoms roll over each If another metal is mixed, it’s not easy for the atoms roll over each other. That’s why the other. That’s why the alloys are harder than pure metalsalloys are harder than pure metals..

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Because of the Because of the electron seaelectron sea, , metals have metals have lustrouslustrous appearance since electrons can appearance since electrons can vibrate at the frequency of the vibrate at the frequency of the light.light.

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REFERENCESREFERENCES

VIRTUAL CHEMBOOKVIRTUAL CHEMBOOK http://www.elmhurst.edu/%7Echm/vchembook/index.html

Gary L. Bertrand Department of Chemistry University of Missouri-Rolla

chemguideHelping you to understand Chemistry Jim Clark 2005 http://www.chemguide.co.uk/ Minerals http://www.uwgb.edu/dutchs/EarthSC202Notes/minerals.htm

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