structure

Chemistry: Structure.
Metallic bonding.
Metallic bonding is the array of positive ions surrounded by sea of free mobile electrons.
Metals are strong because of the powerful attraction between the positive centres and the free electrons.
Metals can conduct electricity because the free electrons can move through out the structure carrying heat energy.
Metals are malleable and ductile because the layers of atoms can slide over each other when force is applied.
An alloy is a mixture of metals
Example of alloy: brass [mixture of copper & zinc]
Alloys are hard because in alloys, the different metals have slightly different size. This breaks up the regular arrangement & makes it more difficult for the layers to slide.

Structure of Diamond

Diamond & graphite are having a giant co-valent structure.
In diamond, each carbon atom is strongly co-valently bonded with four other carbon atoms leading to a three dimentional network.
Diamond is hard due to the strong carbon-carbon co-valent bonds.
Diamond does not conduct electricity because all the electrons in the outer level of the carbon atoms are tightly held in co-valent bonds between the atoms. So no free electrons to move around and carry electricity.
Diamond does not dissolve in water or any other solvents because of the powerful co-valent bonds between the atoms.
Diamond is used in cutting concrete and glass because it is hard.
Diamond is used for making jewellery because it is shiny in nature.
Diamond is having a high sublimation point because of the strong co-valent bonds between the carbon atoms.

Structure of graphite

In graphite, each carbon atom is strongly co-valently bonded to three other carbon atoms leading to a hexagonal ring. Graphite has a layer structure and the layers are held by weak vanderwall’s force of attraction.
Graphite can conduct electricity because each carbon atom is strongly co-valently bonded to three other carbon atoms leaving an electron free. This free electron can carry electricity through out the structure.
Graphite is soft because the layers can slide over each other with the help of weak vanderwall’s force of attraction.
Graphite is not soluble in any solvent because of the strong co-valent bonding between the carbon atoms in the hexagonal ring.
Graphite is having a high sublimation point because of the strong co-valent bond between the carbon atoms.
Allotropy: some elements occur in more than one physical form. Eg: carbon (diamond & graphite).

Structure of sodium chloride.

Sodium chloride is having a giant ionic structure.
In solid sodium chloride, each sodium ion [Na+] is surrounded by 6 other chloride ion [Cl-] with strong electrostatic force of attraction.
Sodium chloride is having high melting point due to the strong electrostatic force of attraction between the ions.
Sodium chloride does not conduct electricity because the ions are held by strong electrostatic force of attraction. They are not free to move.
Sodium chloride conduct electricity in liquid state because the ions are free to move and can carry electricity.

Simple molecular structure

The molecules exist in simple molecules and weak force of attraction held them together. So they may be solid, liquid, or gas.
Simple molecules have low melting & boiling point due to the weak intermolecular force of attraction.
Ice, solid iodine, & solid carbondioxide are examples of simple molecular crystals. They have low melting point due to the weak intermolecular force.
Carbondioxide shape: linear.
Methane shape: tetrahydral.
Water shape: non-linear.
Ammonia shape: pyramidal.