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In ice, hydrogen bonds between the water molecules hold them together in a fairly open tetrahedral structure while the strong bonds within the water molecules are polar covalent.

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Giant ionic structures e.g chloride are generally hard, brittle & high melting due to the strong ionic bonds. No electrical conductivity in solids since ions are fixed in the crystal. In molten salt or aqueous solutions they conduct as they're free to move when a voltage is applied.
Giant covalent structures(diamond&graphite) are very high melting & insoluble in water; diamond is hard with each carbon covalently bonded to 4 other, but the weak layer structure in graphite make it softer & useful as a lubricant. Also graphite conducts electricity. Iodine is volatile and soft as I₂ units are held together by weak van der Waals forces.
Electron delocalisation in metals gives it good electrical & thermal conductivity but their melting temperature & hardness increase with the number of electrons per atom involved in bonding.

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The malleability & ductility of metals is explained by the electron 'sea' model because the 'sea' of electrons allows layers of cations to slide passed each other. Therefore metals aren't brittle.

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The model describes metals as containing positive ions bonded together by their attraction to a 'sea' of electrons. This is metallic bonding.
Electrical conductivity -
the free electrons allow a current to pass through the metal.
Thermal conductivity -
the free electrons can carry thermal energy around the lattice.

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Iodine molecules are held in a molecular crystal lattice by weak Van der Waals forces.
Solid iodine is very volatile (evaporates easily); it easily changes from a solid straight into a vapour - a process called sublimation.

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Diamond
Tetrahedral, strong covalent arrangement . Diamond is strong because it has 4 covalent bonds( 8 electrons in outer shell) - it's stable.
Graphite
Layers made up of covalent hexagons(trigonal planar) which are held together by weak van der Waals forces. In this form, carbon only makes 3 covalent bonds making one electron delocalised. This explains why graphite conducts & diamond doesn't even though they are both allotropes of carbon.

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Cation - positive ion
Anion - negative ion

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The crystal coordination numbers are 8:8 in CsCl & 6:6 in NaCl.
Ions of opposite charge pack around one another to increase bonding energy by maximising electrostatic attraction & minimising repulsion.
Caesium Chloride (CsCl) has higher co-ordination numbers than Sodium Chloride (NaCl) because the Caesium cation Is larger than the sodium cation meaning that caesium can accommodate more chlorine anions.
The coordinate number of an ion in a crystal lattice is the number of nearest neighbours of opposite charges.