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Chapter 7 - Periodicity II - Coggle Diagram
Chapter 7 - Periodicity II
Metals
Metallic bonding
Each atom has donated its negative outer shell electrons to a shared poll of electrons, which are delocalised through the structure
Positive ions left behind consist of the nucleus and inner electrons shells of the metals atoms
Strong electrostatic force of attraction between cations and a sea of delocalised electrons
Cations are fixed in position, which maintains the shape
Delocalised electrons are mobile and able to move
Properties
Strong metallic bond - attraction between positive ions and delocalised electrons
High electrical conductivity
High melting/ boiling points
Electrical conductivity
Metals conduct electricity when solid and liquid
When there is voltage, delocalised electrons can move through the structure and carry charge
Melting/ boiling points
Most metals have high melting/ boiling points
High temperature is necessary to provide the large amount of energy needed to overcome strong electrostatic attraction between cations and electrons
Most metals having high melting/ boiling points
Solubility
Metals don't dissolve
Any interaction between polar solvents would lead to a reaction
Giant Covalent structures
Typical properties
Strong covalent bonds
Stable structures that are difficult to break down
Melting/boiling points
High melting/boiling points
High temperatures are necessary to provide the large quantity of energy needed to break the strong covalent bonds
Solubilty
Giant covalent lattices are insoluble in most solvents
Covalent bonds holding atoms together are too strong to be broken by interation with solvents
Conductivity
Giant lattices are non conductors, the only exception are graphene and graphite, which are forms of carbon
In Diamond and silicon, all foru outer shell electrons are invovled in a bond, so none are available for conducting
Carbon is special in forming structures where one of the electrons in available for conductivity
Graphene and Graphite
Apart from diamond, carbon forms giant covalent structures based on planar hexagonal layers
Three of the four electrons are used in covalent bonding
Remaining electron is released into a pool of delocalised electrons shared by all atoms
Graphite
Composed of parallel layers of hexagonally arranged carbon atoms
Layers are bonded by weak London forces
Bonding in hexagonal layers used three of the four electrons
Spare electron is delocalised between the layers
Can conduct electricity
Graphene
Single layer of graphite
Composed of hexagonally arranged carbon atoms in strong covalent bonds
Same electrical conductivity as copper
Thinnest and strongest material
Periodic trend in melting points
Across period 2 and 3
Melting point increases group group 1-4(14)
Sharp decrease in melting points between group 4(14) and 5(15)
Melting points are low from group 5(15) to 0(18)
Sharp decrease in melting points marks a change from giant to simple molecular structures
Giant melattic structures - strong metallic bonds between cations and delocalised electrons
Giant covalent structures - strong covalent bonds between atoms
Simple molecular structure - weak London forces between molecules