2.2.7 Giant Covalent Structures

what are allotropes

different molecular arrangements of the same atom

what are the allotropes of carbon (4)

graphene

graphite

buckminster fullerene

diamond

what is a giant covalent network structure

3D structure where atoms are bonded covalently and indefinitely, forming a large lattice. No individual molecules.

describe the strucutre and bondign of diamond

each carbon atom covalently bonded to 4 other carbon atoms to form a tetrahedral structure with a bond angle of 109.5

describe the strucutre and bonding of grpahite

each carbon atom bonded to 3 other carbon atoms to form hexagonal layers with bond angles of 120, trigonal planar. layers are held together by weak intermoleucular forces

describe the structure and bonding of buckminster fullerene

contains 60 carbon atoms with each carbon atom bonding to 3 other c atoms. 4 electron delocalised so electrons can migrate through the strucutre

12 pentagons and 20 hexagons

describe the structure and bonding in graphene

single layer of carbon atoms (single layer of groahite) with each carbon atom bonded covalently to 3 other carbon atoms to form hexagons

describe the structure and bonding of silicon

tetrahedral arrangement like diamond and 109.5 bond angle, with each silicon atom covalentyl bonding to 4 other silicon atoms to form a giant lattice structure

descibe the structure of silicon (IV) dioxide (sand od silicon dioxide)

same structure of diamonds: gaint tetrahedral strucutre all bonded covalently with 109.5 bond angle

each silicon bonds to 4 oxygens and each oxygen bonds to 2 silicons

what is the empiricial formula of diamond

SiO2

dogianto covalent networks have high or low melting and boiling points and why

high because they have strong covalent bonds throughout which require lots of energy to overcome

is graphite soft or hard and why

soft becuse regular layers can slide over each other as a result of weak intermoleuclar forces

are diamond and silicon dioxide hard or soft and why

hard because difficult to break strong network of covalent bonds

why can graphite and graphene conduct electricity

have delocalised electrons between carbon layers as each c atom ony bonded to 3, not 4 so electron can carry a charge throught the structure

why do diamond and silicon dioxide not conduct electricity

all 4 electrons of every atom are part of covalent bond so no free electrons availible

table of properties