covalent bonding Flashcards
define single covalent bond
contains a shared pair of electrons
define a multiple covalent bond
shares multiple pairs of electrons
what does a bond show in terms of electrons
a bond shows a shared pair of electrons between 2 atoms
what is a lone pair of electrons shown as in lewis structures
lone pair of electrons is shown by 2 dots
define compound oxyanion
negatively charged ions where oxygen is bonded to the central atom
what do group 7 elements break when they are the central atom
the octet rule
what do you do with the charge on ions with lone pairs on the central atom
if an oxygens put them charge on them if not put the charge on the central atom
define dative covalent bond
both bonding electrons come from 1 element and is represented by an arrow
formed from atoms with a lone pair of electrons
in diamond how many covalent bonds does each carbon atom form
4 covalent bonds
what shape does diamond have and give the bond angle
tetrahedral
109.5
in graphite how many covalent bonds does each carbon atom form
3 covalent bonds
what molecular shape does graphite have and give the bond angle
trigonal planar
120 degrees
why does graphite conduct electricity
due to its delocalised electrons which can travel freely and allowing graphite to conduct electricity along the hexagonal planes
why is graphite used in pencils
the weak Van Der Waals forces allow the layers to slide over each other making graphite soft and flaky
why do ionic compounds only conduct electricity when aqueous or molten
as the ions are free to move and carry charge through the structure
define simple molecular structure
small groups of atoms held together by covalent bonding
define macromolecular structure
large numbers of atoms are link in regular 3d arrangements by covalent bonds
define giant ionic structure
a lattice of positive and negative ions surrounding each other
define metallic structure
regular lattice of positively charged metal ions held together by a cloud of delocalised electrons
Describe the structure and bonding in graphite and explain why the melting point of graphite is very high (5 marks)
layers of carbon atoms
with 3 covalent bonds to each carbon atom
Van der Waals forces between the layers
lots of very strong covalent bonds need to be broken
this requires lots of energy
Explain why graphite is a good conductor of electricity
(3 marks)
1 spare electron per carbon atom
delocalised between layers
can flow between layers and carry charge
The diagram shows the arrangement of some of the water molecules in a crystal of ice. Give one reason why ice is less dense that water
Water molecules in ice are held further apart due to hydrogen bonds
