25 may 2010 - diamond , graphite , silicon dioxide

well these are something to refresh your mind. still remember about those structure? diamond , graphite , silicon dioxide ?

well i know its not that clear but try to squint for the STRUCTURE ONLY.

left : DIAMOND

centre : GRAPHITE

right : SILICON DIOXIDE

DIAMOND 

formula : C

structure :

• each carbon atom is join to four other atoms by strong covalent bonds in a tetrahedral arrangement.

properties : 

• very high melting points 
• very poor conductivity of electricity
• very hard 

DIAMOND IS VERY HARD dye to the strong covalent bonds in a giant structure.

GRAPHITE

formula : C

structure :

• consist of flat layers of carbon atoms. each carbon atom is joined to three others by strong covalent bonds. There are no covalent bonds between the layers. 

properties :

• very high melting point
• conducts electricity
• soft

GRAPHITE IS SOFT as the layers of atoms can easily slide over each other.

SILICON DIOXIDE

formula : SiO2

structure : 

• each silicon atom is joined to four oxygen atoms by strong covalent bonds. Each two silicon atoms.

properties :

• very high melting point
• very poor conductor of electricity
• HARD (but not as hard as diamond)

SILICON DIOXIDE IS HARD due to the strong bonds in a giant structure.

good night.

all credits goes to : admin and a-level's notes.