Structure and bonding Flashcards
what is an ionic bond
particles are oppositely charged ions
occurs in compounds formed in metals combined with non metals
what is a covalent bond
particles are atoms which share pairs of electrons
occurs in most non metallic elements and in compounds of non metals
what is a metallic bond
particles are atoms which share delocalised electrons
occurs in metallic elements and alloys
describe the bonding in magnesium oxide
magnesium loses 2 electrons to become 2+ ion
oxygen gains 2 electrons to become 2- ion
magnesium transfers the 2 electrons to oxygen
there is an electrostatic attraction between the oppositely charged ions
this forms an ionic bond
why do ionic compounds have a high melting point
strong electrostatic attraction between oppositely charged ions
stops them moving further apart
needs a lot of energy to break the bond
why are ionic compounds soluble
the ions can separate in water
why do ionic compounds not conduct electricity as a solid
ions are fixed in the lattice structure and can’t move
what are ionic compounds
giant lattice structure of ions
held together by electrostatic forces of attraction between oppositely charged ions
why do ionic compounds conduct electricity as a solution
ions can move in water
what is small covalent bonding
contain a few bonded atoms
what is giant covalent bonding
millions of atoms are joined together
describe the bonding between hydrogen and chlorine
hydrogen has 1 electron in outer shell
chlorine has 7 electrons in outer shell
to get full outer shell , hydrogen and chlorine share an electron each
the sharing of a pair of electrons is called a covalent bond
why do small covalent structures have a low melting point
weak intermolecular forces
takes a small amount of energy to break them
why do small covalent structures not conduct electricity
molecules have no charge and are neutral
molecules cannot move and conduct electricity
what are the properties of diamond
giant covalent
each carbon is bonded to 4 others
lots of strong bonds
why does diamond not conduct electricity
no delocalised electrons that can move
why does diamond have a high melting point
strong covalent bonds as each carbon bonded to 4 others, needs a lot of energy to break
what are the properties of graphite
soft/slippery
made of layers
weak intermolecular forces
each carbon bonded to 3 others
delocalised electrons
why is graphite soft and slippery
layers can slide over each other because there are weak forces between them
why can graphite conduct electriciy
delocalised electrons that can move through the whole structure
why does graphite have a high melting point
giant structure lots of covalent bonds
each carbon bonded to 3 others
needs a lot of energy to break bonds
what are the properties of silicon dioxide
each silicon is bonded to 4 oxygens
why is silicon dioxide hard
giant structure and has lots of covalent bonds
why does silicon dioxide not conduct electricity
no delocalised electrons that can move
why does silicon dioxide have a high melting point
many strong covalent bonds and needs a lot of energy to break
what are the similarities between graphite and graphene
both giant covalent
both made of carbon
both have carbon bonded to 3 others
both have delocalised electrons
both have hexagonal structure
what are the differences between graphite and graphene
graphite has layers whereas graphene has only one layer
why is graphene strong
lots of strong covalent bonds carbon bonded to 3 others
why does graphene conduct electricity
delocalised electrons that can move through the structure
what is an allotrope
different physical forms of an element
what can carbon form
cage like structure called a bucky ball (buckminster fullerene)
what can graphene form
tube like structure called a nanotube
what are the properties of polymers
very large molecules
atoms in polymer molecules are linked to other atoms by covalent bonds
intermolecular forces are strong so they are solids at 20 degrees
how big are nanoparticles
1-100 nano meters across
contain a few hundred atoms
how big is a nanometre
1 x 10-9
what are the properties of nanoparticles
large sa
react faster than normal sized particles
smaller than fine particles
what are nanoparticles used for
catalysts
in socks
suntan cream
tennis balls
sensors
building materials
lubricant coatings
how do you work out surface area
(length x width) x number of faces
why does a nanoparticle have different properties to the bulk chemical its made from
high surface area to volume ratio
what are the disadvantages of nanoparticles
may be toxic
may be able to enter the brain from the bloodstream and cause harm
what are the structures of metallic substances
lattice structure
electrons in outer shell of metal atoms are delocalised
strong forces of attraction between positive metal ions and negative electrons
why do metallic substances have high melting and boiling points
strong electrostatic attraction between the metal atoms and delocalised electrons
needs a lot of energy to break
why are metallic substances good electrical conductors
delocalised electrons can carry charge and move freely through the metal
why are metallic substances good thermal conductors
when a metal is heated the delocalised electrons gain kinetic energy and move faster
this movement transfers the gained energy through the metal
why are metallic substances malleable
pure metals are soft
layers of metal ions are able to slide
what is an alloy
a mixture of two or more different metals
not a compound because the metals do not react together
other metal distorts the layers so they cannot slide over each other
now the alloy is harder
what are polymers
lots of small units linked together to form a long molecule that has repeating sections
all the atoms in a polymer are joined by strong covalent bonds
what is a hydroxide ion
OH-
what is a nitrate ion
NO -
3
what is a sulfate ion
SO 2-
4
what is a carbonate ion
CO 2-
3
what three things affects how strong the forces of attraction are between particles
material
temperature
pressure
how close are the particles in solids
very close in a very regular pattern
what are the forces of attraction like between solid particles
strong forces of attraction
how do the particles move in a solid
can’t move but vibrate around a fixed point
what are the energy levels like of a solid particle
low energy
how close are the particles in a liquid
close together but irregular pattern
what are the forces of attraction like in a liquid
small forces
how do the particles move in a liquid
move in any direction
what is the energy level of particles in a liquid
lower than gases
higher than liquids
how close are particles in a gas
far apart
how close are particles of a gas
far apart
what are the forces of attraction like between gas particles
no forces of attraction
how do particles move in a gas
any direction
what is the energy level of particles in a gas
high
