Chemical Bonding: Ionic Bonding Flashcards
what is ionic bonding?
electrostatic attraction between positive ions and negative ions
which groups are involved
occurs between a metal (group 1,2,3) and a non-metal (group 6,7)
why are electrons transferred?
to complete the outer shell
how is ionic bonding represented?
in dot and cross diagrams
how is sodium chloride held together?
by strong electrostatic attraction
in sodium chloride is it called a chloride atom or a chlorine atom?
chloride
in energy released or absorbed when bonding occurs?
released
draw the dot and cross diagram for sodium chloride NaCl
a single electron on outer shell of sodium has been transferred to chlorine
what is the noble gas structure significance?
some ionic structures are similar to noble gas structures
e.g. magnesium oxide, sodium chloride
what is the struture of ionic bonds?
how is it held together?
giant ionic structures
a huge lattice of positive and negative ions packed together in a regular way
held together by the strong attractions between the positive and negative ions
what is a lattice?
a regular array of particles
what is the giant ionic structure of sodium chloride?
each sodium ion is touched by six chloride ions
each chloride ion is touched by six sodium ions
only ions joined together in Figure 4.12 are touching
this structure repeats itself over vast numbers of ions
(note the lines just show the arrangement of atoms)
although they have the exact same structure, is magnesium oxide’s lattice held together by a stronger attraction that sodium chloride? why?
yes
the ions have a higher charge and therefore a higher attraction
do they tend to be hard or soft solids?
hard
do they tend to be crystalline? why?
because of the regular arrangement of ions in the lattice
some crystals are too small to be seen
e.g. magnesium oxide is seen as white powder because the individual crystals are too small to be seen by the naked eye
do they have high or low melting points and boiling points? why?
yes
because of the strong forces holding the lattice together
do they tend to be brittle or ductile?
brittle
because any small distortion of a crystal will bring ions with the same charge against each other
like charges repel and so the crystal splits itself in half
do they tend to be soluble or insolube in water? why?
soluble
although water is a covalent molecule, the electrons in the bond are attracted to the oxygen end of the bond
this makes oxygen slightly negative
this leaves hydrogen slightly short of electrons, therefore slightly positive
water is therefore described as a polar molecule
there are quite strong attractions between polar water molecules and the ions in the lattice
the slightly positive hydrogens in the water molecule cluster around the negative ions
the slightly negative oxygens are attracted to the positive ions
the water molecules then pull the sodium chloride apart
magnesium oxide isn’t soluble in water because the attractions between the ions aren’t strong enough to break the very powerful ionic bonds between magnesium and oxide ions
do they tend to be soluble or insoluble in organic substances? why?
soluble
organic solvents contain molecules which have much less distortion than there is in water
their molecules are less polar
there is not enough attraction between these molecules and the ions in the crystal to break the strong forces holding the lattice together
what is conductivity?
flow of charge
flow of electrons/ions
do ionic substabces conduct electricity in solid state? why?
no because they don’t contain electrons that can move
they do conduct when molten or in dissolved in water because ions are free to move around
what are the uses of some ionic substances?
Sodium fluoride prevents tooth decay
Silver halides are used in photographic film
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the higher the charge the …. the melting point
the higher the charge the higher the melting point
what is the diagram for Potassium Fluoride, KF
what is the diagram for aluminium chloride, AlCl3
what is the diagram for Lithium Oxide, Li2O
