Structure and Bonding Flashcards
when does ionic bonding occur
when a outer shell electrons from a metal atom transfer to fill the outer shell of a non-metal atom
how does an ionic compound form
The metal (magnesium) loses (2) electrons and become cations The nonmetal (chlorine) each gain one electron and become anions so they all have full outer shell The positive ions are attracted to the negative ions and have an electrostatic attraction between them
describe the bonding in an ionic compound
strong electrostatic attractions between the oppositely charged ions which extend across a giant lattice
coordination number
how many negative ions each positive ion is bonded to
factors affecting strength of ionic bonds
charge on the ions
size of ions (increase in radius decreases charge density so weaker attraction)
properties of ionic compounds
high melting point non conductive when solid conductive when aq/molten brittle soluble in water
describe the structure of ionic compounds
giant lattice which extends in all directions
why do ionic compounds have a high melting point
millions of strong electrostatic attractions between the oppositely charged ions in the giant lattice which require a lot of energy to break
why do ionic compounds not conduct when solid
ions are fixed in a giant lattice so the ions are not free to move to their oppositely charged electrode
why do ionic compounds conduct when aq/molten form
ions are free to move to their oppositely charged electrode and carry a charge
why are ionic compounds brittle
a sharp blow displaces ions so the ions with like charges come in contact with each other causing the structure to shatter
why are ionic compounds soluble in water
ions break apart from the giant lattice as water is a polar molecules so can overcome the electrostatic attractions between the oppositely charged ions
how does covalent bonding occur
non-metal ions share electrons
examples of molecules with covalent bonding
simple molecules
macromolecules
what is dative bonding
when the shared pair of electrons come from the same atom
one species must have a lone pair of electrons
other species must have a vacant orbital to accept the lone pair
properties of simple molecules
low melting point
non-conductive
weak
insoluble in water
why do simple molecules have a low melting point
weak intermolecular forces between the molecules require little energy to break
are there any exceptions to simple molecules having low melting points
water has a high melting point for its Mr
has hydrogen bonds between the molecules which are the strongest type of intermolecular force
why are simple molecules non-conductive
no free ions or delocalised electrons that could carry a charge
why are simple molecules weak
weak intermolecular forces between the molecules require little force to break them apart
why are simple molecules insoluble in water
non-polar molecule so no interactions with water
why is ice more dense than water
hydrogen bonds hold h2o molecules far apart when solid
broken hydrogen bonds means that the molecules can be closer together
properties of diamond
high melting point
hard
non-conductive
insoluble
shape of diamond and bond angle
tetrahedral 109.5
why does diamond have a high melting point and is hard
millions of strong covalent bonds between the millions of carbon atoms in the rigid macromolecular structure which requires a lot of energy to break
why is diamond non-conductive
each carbon atom is bonded to 4 carbon atoms by strong covalent bonds so there are no delocalised electrons that can flow throughout the structure
why is diamond insoluble
strong covalent bonds do not break apart as the macromolecular structure is non-polar so the atoms are not attracted to the polar molecule