giant covalent structrues

Question 1

define giant covalent structures

Answer 1

contain very many atoms joined together by strong covalent bonds
giant molecular crystal is an irregular three dimensional arrangement of atoms

Question 2

what are diamond and graphite

Answer 2

allotropes of carbon

Question 3

define allotropes

Answer 3

made up of same element but different structural form of an element in same physical state

Question 4

explain the difference between diamond and graphite

Answer 4

diamond hardest substance on earth but graphite is easily breakable
diamond - jewellery
graphite - used in pencils
both have carbon atoms joined by strong covalent bonds but in such different arrangements that physical properties are different

Question 5

define graphite

Answer 5

giant covalent structure in which each carbon atom is bonded to three other atoms by covalent bonds
carbon forms layers with hexagonal arrangement of atoms
weak intermolecular form exist between layers
each carbon atom has one outer electron which becomes delocalised as it is not involved in bonding

Question 6

define graphite

Answer 6

each carbon atom forms four covalent bonds with four other carbon atoms to form 3d tetrahedral structure
also described as giant atomic structure

Question 7

appearance

Answer 7

diamond - transparent and sparkling
graphite - black opaque shiny

Question 8

melting point

Answer 8

very high for both due to very string covalent bonds between carbon atoms

Question 9

electrical conductivity

Answer 9

diamond - non conductor as no free electrons to move and carry an electric current
graphite - conductor as free electrons to move and carry electirict because only three of carbon atoms are bonded

Question 10

hardness

Answer 10

diamond - extremely hard
graphite - soft and flaky

Question 11

lubricating power

Answer 11

diamond - none
graphite extremely good due to weak forces between layers which allow them to slide over each other