topic 1 - structure and bonding Flashcards
ion
a charge particle
anion
a negative ion
formed through electron gain
what groups form anions
6 and 7
cation
a positive ion
formed through electron loss
what groups readily form cations
1 and 2
how is an ionic bond formed
a metal atom loses electrons to form a cation
a non metal atom gains these electrons to form an anion
the two oppositely charged ions are strongly attracted to one another by ELECTROSTATIC FORCES
ions ending in -ate
negative
contain oxygen and at least one other element
ions ending in -ide
negative
only contain one element (excluding hydroxide)
structure of ionic compounds
regular, giant ionic lattice held together by strong electrostatic forces between oppositely charged ions
properties of ionic compounds
high melting and boiling points
conduct electricity when molten or aqueous
why do ionic compounds have high melting and boiling points
takes a lot of energy to overcome the strong electrostatic attraction
why do ionic compounds conduct electricity when molten or aqueous
when solid, the ions are held in place so can’t conduct electricity
when molten/aqueous, ions are free to move and therefore can carry electric current
covalent bond
a strong bond formed when a pair of electrons is shared between two atoms
covalent bond features
weak intermolecular forces
uses non metal atoms
creates molecules
properties of simple covalent compounds
low melting and boiling points
poor conduction of electricty
why do simple covalent compounds have low melting and boiling point
the intermolecular forces are weak so not much energy is needed to overcome them
why do simple covalent compounds not conduct electricity well
they contain uncharged atoms so there are no free ions or electrons to carry the current
properties of giant covalent structures
very high melting and boiling points
don’t conduct electricity (apart from graphite and graphene)
insoluble in water
what giant covalent structures can conduct electricity
graphite
graphene
why do giant covalent structures have VERY high melting and boiling points
lots of energy is needed to overcome the strong covalent bonds
give 4 examples of giant covalent structures
diamond
graphite
graphene
C60 - buckminsterfullerene
diamond
network of carbon atoms that each form 4 covalent bonds
properties of diamond and their reasons
high melting and boiling points - strong covalent bonds (strong intermolecular forces)
very hard - strong, rigid lattice structure
no conduction of electricity - no free ions or electrons
use of diamond
cutting tools
graphite
a carbon structure where carbon atoms have three covalent bonds and the 4th electron is delocalised
this creates sheets of carbon atoms arranged in hexagons
properties of graphite and their reasons
high melting point - strong covalent bonds (strong intermolecular forces)
conduction of electricity - the delocalised electron is free to move
soft and slippery - layers don’t have covalent bonds between them, allowing them to slide over one another
uses of graphite
electrodes
lubrication
allotrope
multiple forms of the same element
fullerene
carbon molecules shaped like a tube/cylinder or hollow ball
can trap molecules
graphene
one layer of graphite
properties of graphene
high melting point
conducts electricity
what can graphene form and what can that be used for
can form carbon nanotubes
these have high tensile strength
used to strengthen lightweight sports equipment
what does C60 look like
hollow sphere
20 hexagons
12 pentagons
polymer
large molecules containing long chains of covalently bonded carbon atoms
formed by lots of monomers joining together
metallic bond
bond between metal ions and delocalised electrons due to electrostatic attraction
physical properties of metals
shiny solids high melting points high density good electrical conductors malleable
why are metals malleable
layers of pure metal can slide over one another
what are the 4 kind of models
2D representations
dot and cross
3D models
ball and stick models
evaluate 2d representations (2+, 2-)
simple and great
shows how atoms are connected
don’t show shape of substance
no indication of atom size
evaluate dot and cross models
shows how compounds are formed
shows where electrons/ions came from
no indication of atom size
no indication of atom arrangement
evaluate 3d models
shows arrangement of ions
only shows the outer layer of a substance
evaluate ball and stick models
shows how the atoms are connected
good for visualising structures
makes it look like there are large gaps between atoms
doesn’t show correct scales of atoms or ions
