structure and bonding Flashcards
when is an ion formed?
when an atom loses or gains an electron. trying to get a full outer shell
metals lose electrons to form positive ions.
non metals gain electrons to form negative ions.
what groups are most likely to form ions.
1 2 6 7.
what is ionic bonding?
a metal loses an electron and a non metal gains an electron.
the opposite ion charges attract.
what does a dot and cross diagram show?
the arrangement of electrons in an atom or ion.
what is the structure of an ionic compound?
a giant ionic lattice.
why do ionic lattices form?
ions form a closely packed lattice with strong forces of attraction between ions in all directions.
what are the properties of ionic compounds?
high melting and boiling point. due to many strong bonds
can’t conduct electricity as a solid. ions are held in place
some can dissolve in water.
what is covalent bonding?
non metal atoms share pairs of electrons. in their outer shells
what are the 2 ways to draw covalent bonds?
dot and cross diagram.
displayed formula.
what is a simple molecular substance? and 7 examples
substances made of molecules containing a few atoms joined by covalent bonds.
hydrogen. H₂
chlorine. Cl₂
oxygen. O₂
nitrogen. N₂
methane. CH₄
water. H₂O
hydrogen chloride. HCL
what are the properties of simple molecular substances?
atoms within molecules are help by strong covalent bonds but forces between molecules are weak.
low melting and boiling points.
most substances are gas or liquid at room temperature.
size increases force strength. increases melting and boiling point
don’t conduct electricity there is no free electrons
what is a polymer?
a large molecule made of small units. called monomers
how are all atoms in a polymer joined?
covalent bonds.
how do you draw a polymer?
draw the smallest repeating unit in brackets and put an n outside.
what is a giant covalent structure?
a large number of atoms joined by covalent bonds.
what are the properties of a giant covalent structure?
very high melting and boiling point. lots of energy is needed to break bonds
do not conduct electricity. no free electrons
what are 3 giant covalent structures? that you have to know
diamond. each carbon atom forms 4 covalent bonds
graphite. each carbon atom forms 3 covalent bonds to create layers of hexagons with 1 free electron
silicon dioxide. silica a giant structure of silicon and oxygen
what is an allotrope?
a structural form an element can exist in.
what is graphene?
a hexagonal sheet of carbon atoms one atom thick.
why is diamond so hard?
diamond is made of carbon atoms each with 4 covalent bonds meaning a lot of energy is required to break it.
what is graphite?
many layers of graphene weakly held together. which makes it good for lubrication
what is a fullerene?
molecules of carbon shaped like closed tubes or hollow balls.
what are fullerenes made of?
hexagons or pentagons or heptagons of carbon atoms.
what can fullerenes be used for?
caging other molecules.
industrial catalysts. catalyst molecules can be attached to the fullerenes
lubricants.
how does metallic bonding work?
electrons in the outer shell of metal atoms are delocalised. free to move around
strong forces of electrostatic attraction between metal ions and electrons hold atoms together in a strong regular structure.
why do metals have high melting points?
forces between atoms and electrons need lots of energy to be broken.
why are metals good conductors?
delocalised electrons carry electric charge and thermal energy.
what does malleable mean?
can be bent hammered or rolled.
why are metals malleable?
layers of atoms can slide over each other.
what is an alloy and why aren’t they malleable?
alloys are metals mixed with other elements.
they are not malleable as they contain different sized atoms which cannot slide over eachother.
