Types of interactions Types of interactions

As a results of these interactions:As a results of these interactions:

1.1. Strong interactions (chemical bonds: Strong interactions (chemical bonds: the the attraction forces are extremely dominant attraction forces are extremely dominant over the repulsion forces)over the repulsion forces)

a)a) Ionic bondsIonic bonds

b)b)Covalent bondsCovalent bonds

c)c) Metallic bondMetallic bond

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Types of interactions Types of interactions

2. Weak interactions (physical bonds : 2. Weak interactions (physical bonds : the the difference b/ the attraction & repulsion forces difference b/ the attraction & repulsion forces is slightis slight)

a)a) Van der Waals bondsVan der Waals bonds

a.1a.1 Dipole-dipole Dipole-dipole

a.2a.2 Ion-dipol Ion-dipol

a.3a.3 Induced dipole (Ion-induced dipole, dipole- Induced dipole (Ion-induced dipole, dipole-induced dipole, London forces)induced dipole, London forces)

b)b) Hydrogen bond Hydrogen bond22

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, making the Many unfilled orbitals, making the valence electrons delocalized(shared valence electrons delocalized(shared by) amongst all the atoms and they are by) amongst all the atoms and they are free to move throughout the metal.free to 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 positively charged metal ions and mobile electrons.

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Metallic bonding in sodiumMetallic bonding in sodiumThe electrons can The electrons can move freely within move freely within these molecular these molecular orbitals, and so each orbitals, and so each electron becomes electron becomes detached from its detached from its parent atom. The parent atom. The electrons are said to electrons are said to be be delocalised.delocalised. The The metal is held together metal is held together by the strong forces of by the strong forces of attraction between the attraction between the positive nuclei and the positive nuclei 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 array of positive ions in a "an array of positive ions in a sea of electrons".sea of electrons".If you are going to use this view, If you are going to use this view, beware! Is a metal made up of beware! Is a metal made up of atoms or ions? It is made of atoms or ions? It is made of atoms.atoms.Each positive centre in the Each positive centre in the diagram represents all the rest diagram represents all the rest of the atom apart from the outer of the atom apart from the outer electron, but that electron hasn't electron, but that electron hasn't been lost - it may no longer have been lost - it may no longer have an attachment to a particular an attachment to a particular atom, but it's still there in the atom, but it's still there in the structure. Sodium metal is structure. Sodium metal is therefore written as Na - therefore written as Na - not not NaNa++ or potassium metal is written as or potassium metal is written as K but not KK but not K++..

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Metallic bond strengthMetallic bond strength

Depends onDepends on

1)1)Valence electron number of the Valence electron number of the metalmetal

2)2)Atomic radii of the metalAtomic radii of the metal

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In periodic tableIn periodic table;;

Metallic bond strength increases

Metallic bond strength decreases.

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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 high melting and boiling points points because of the strength of the metallic because of the strength of the metallic bond. bond. Group 1 metals like sodium and potassium have Group 1 metals like sodium and potassium have relatively low melting and boiling points mainly relatively low melting and boiling points mainly because each atom only has one electron to because each atom only has one electron to contribute to the bond.contribute to the bond.They have relatively large atoms (meaning that They have relatively large atoms (meaning that the nuclei are some distance from the the nuclei are some distance from the delocalised electrons) which also weakens the delocalised electrons) which also weakens the bond.bond.

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The physical properties of metalsThe physical properties of metals

Electrical conductivityElectrical conductivityMetals conduct electricity. The Metals conduct electricity. The delocalised electrons are free to delocalised electrons are free to movemoveLiquid metals also conduct Liquid metals also conduct electricity, showing that although electricity, showing that although the metal atoms may be free to the metal atoms may be free to move, the delocalisation remains move, the delocalisation remains in force until the metal boils.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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Since the motion of electrons is easier Since the motion of electrons is easier compared to that of ions, metals are compared to that of ions, metals are better conductors of electricity better conductors of electricity compared to ionic compounds.compared to ionic compounds.

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Electrical conductivity of Electrical conductivity of metalsmetals

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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Strength and workabilityStrength and workability

Malleability and ductilityMalleability and ductilityMetals are described as Metals are described as malleable malleable (can be (can be beaten into sheets) and beaten into sheets) and ductile ductile (can be pulled (can be pulled out into wires). out into wires). This is because of the ability of the atoms to This is because of the ability of the atoms to roll over each other into new positions without roll over each other into new positions without breaking the metallic bondbreaking the metallic bond and the electron and the electron seasea..

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As metallic bond strength As metallic bond strength increases, the metallic activity increases, the metallic activity decreases.decreases.

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Because of the electron sea, Because of the electron sea, metals have metals have lustrous appearancelustrous appearance since electrons can vibrate at the since electrons can vibrate at the frequency of the light. This is frequency of the light. This is also the basis for why the mirror also the basis for why the mirror image of an object is exactly the image of an object is exactly the same w/ the object itself.same w/ the object itself.

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Transition metalsTransition metals

Have also got Have also got covalent character covalent character along w/ along w/ the metallic character.the metallic character.

As the As the number of unpaired electrons in d number of unpaired electrons in d orbitals increases, the covalent character orbitals increases, the covalent character for the metal also increases.for the metal also increases.

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V has 3 unpaired electrons and these electrons can overlap w/ other orbitals and make covalent bonds. Although Cr and Mn have bigger number of unpaired electrons, these electrons are not involved in covalent bond making because of having the spherical symmetry. From Mn to Zn, the number of unpaired electrons decreases and so does the melting point and hardness for the metals.

Transition metalsTransition metals

Since Zn has all of its electrons paired, it Since Zn has all of its electrons paired, it has no covalent character, and hence, has has no covalent character, and hence, has the lowest melting point among all the 4the lowest melting point among all the 4thth period transition metals.period transition metals.

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