C2.2 Flashcards
periods
horizontal rows
groups
vertical columns
who created the periodic table?
Mendeleev
ions
charged particles that have either lost or gained electrons
ionic bonding
metal + non-metal
covalent bonding
non-metal + non-metal
describe covalent bonding
-when non metal atoms react, they need to gain electrons to fill their outer shell
-they can only do this if they share their electrons
what are strong covalent bonds a result of?
electrostatic attraction between positive nuclei of the atoms and the pairs of negative electrons that are shared between them
properties of simple covalent bonds
-2 or more non metals
-mostly gases
-low melting and boiling points
-don’t conduct electricity
-low density
why do covalent molecules have a low density?
molecules are not closely packed together
why do covalent molecules have low melting and boiling points?
strong covalent bonds are not what is broken apart it is the weak intermolecular forces between the bonds that is broken
why do covalent molecules have a low conductivity?
there must be free moving charged particles to conduct electricity and covalent molecule have no free moving ions
metal properties
-malleable
-shiny
-sonorous
-conducts electricity and heat
-solid at room temperature
-ductile
-high density
non-metal properties
-not shiny
-brittle
-doesn’t conduct electricity or heat
-variety of states at room temperature
-low density
differences between the old and new periodic table
-fewer elements
-no atomic numbers
-gaps
describe ionic bonding
during a chemical reaction between a metal and a non-metal, the reacting atoms either lose or gain electrons to achieve a full outer shell
metal ions
lose electrons and form cations
non-metal ions
gain electrons and form anions
structure of ionic compounds
-oppositely charged ions are arranged in a regular way to form a giant ionic lattice
what do giant ionic lattices result in?
the formation of crystals
what is the overall net charge of an ionic compound?
it has no overall net charge
properties of ionic compounds
-high melting and boiling points
-conducts electricity when molten or in a solution
-crystalline and brittle
-soluble in water
why do ionic compounds have high melting and boiling points?
the strong ionic bonds must be broken which requires a lot of energy
why do ionic compounds only conduct electricity when molten?
in a solid the ions aren’t free to move, in a solution they are free to move and you need freely moving particles to hold a charge
why are ionic compounds crystalline and brittle?
when you put pressure on the compound, ions who have the same charge come next t each other and repel, causing it to shatter
why are ionic compounds soluble in water?
chloride ions are attracted to the hydrogen ions, the sodium ions are attracted to the oxygen ions and the compounds are separated by the water molecules because of the oppositely charged attraction
malleable
capable of being hammered or pressed into shape without breaking or snapping
ductile
capable of being drawn into thin wires without breaking
metallic bonds
metal + metal
describe metallic bonds
strong electrostatic attraction between delocalised electrons and positive metal ions
what are the properties of metallic bonds?
-high melting and boiling points
-good conductors
-flexible
why do metallic bonds have high melting and boiling points?
they have very strong metallic bonds which require a lot of energy to break
why are metallic bonds good conductors?
delocalised electrons are free to move and carry a charge
why are metal bonds flexible?
the layers can slide over each other which is why they are malleable and ductile
alloy
mixture of two or more metals
allotropes
different forms of the same element that have different properties because their atoms are arranged differently
properties of giant covalent structures
-very high melting and boiling points
-crystalline appearance
-hard
-generally don’t conduct electricity
-insoluble in water
why do covalent structures have high melting and boiling points?
consists of very strong bonds which require a lot of energy to break
why do covalent structures have a crystalline appearance?
ordered in a giant lattice structure
why are covalent structures hard?
made of rigid covalent bonds
why do covalent structures generally not conduct electricity?
every carbon atom is bonded to other carbon atoms so there are no delocalised electrons left over
comparing metals with alloys
metal: has regular layers which means they can slide over each other when stretched or bent
alloys: don’t have regular layers as the different type of metal distorts the layers which makes it harder for layers to slide over each other
what are giant covalent structures?
consists of millions of non-metal atoms joined by covalent bonds and arranged in a repeating regular pattern
what are the different abilities of carbon?
-forms four chemical bonds to other atoms
-bond itself forming long straight, branched and even ring carbon chains
-form single, double or even triple bonds
describe the structure of graphite
-made from repeating hexagons that form layers or sheets
-this leaves each carbon with a ‘spare’ electron that isn’t used in bonding, these spare electrons are free to move between the layers
-this means carbon is bonded to three other carbon atoms
what is an example of a giant covalent structure?
silicone dioxide
what are fullerenes used for?
lubricants
polymers
very long covalent molecules
LDPE
low density polyethene e.g. plastic bags
HDPE
high density polyethene e.g. hard hat
increasing the chain length of polymers
-long polymer chains have stronger intermolecular forces than shorter ones
-by making the chains of polymers longer, a stronger and less flexible material is produced with a higher melting point
modifying polymers using cross linking
-addition of cross links between polymers makes the material tougher, less flexible and increases melting point
-crosslinks are chemical bonds that links polymer chains together
thermosoftening polymer
gets softer when heated
thermosetting polymer
gets harder when heated
limitations to the particle model
-scale of nucleus to the electrons is wrong in most models
-models show bonds as physical structures
-most models do not give an accurate idea of the 3D shape of a molecule
-bond lengths are not in proportion to the size of the atom
what are synthetic polymers commonly called?
plastic
what is an example of a naturally occurring polymer?
silk
how do polymers form?
when lots of small covalent molecules called monomers join together
