C2 Flashcards
What is the mass number in an atom
the total number of protons and neutrons
What is the atomic number of an atom
The number of protons
How do you find the number of neutrins in an atom
subtrace the atomic number from the mass number
How can you tell the atomic number frkm the mass number
the atomic number is never bigger than the mass number
How are compountd formed
When atoms of two or more elements are chemically combined together
is it easy to seperare the atoms that have formed a compound
no
What are isotopes
different atomic forms of the same element, which have the same number of protons but a different number of neutrons
What happens in ionic bonding
In ionic bonding, atoms lose or gain to form charges particles called ions which are then strongly attracted to one another because of the attraction of opposite charges
when would a shell want to get rid of one or more electrons
when the electrons are less than half of the number of electrons it needs to have a full outer shell
What is an ion
an atom with a full outer shell
what lattice strusture do ionic compounds have and why are they strong
giant ionic lattices, they are strong because they have very strong forces electrostatic forces of attraction between oppositely charged ions, in all directions
What similar properties do ionic compounds share?
they all have high melting points and hkgh boiling points due to the strong attraction between the ions. It takes a large ammount of energy to overcome this attraction.
What happens when ionic compounds melt
they are free to move and theyll carry electric current
What happens when ions dissolve
the ions seperate and are all free to move in the solution, so theyll carry electric current
What do ions and noble gases share
they bith have the same electronic structure with a full outer shell
Which atom groups are most likely to form ions and why
group 1,2,6&7 , 1&2 because they are metals and lost electrons to form positive ions and group 6&7 elements are non-metals. They gain electrons to form negative ions.
what are ionic compounds made up of
ionic compounds are made up of a positively charged part and a negatively charged part
what is the overall charge of any compound
0
what structures do ionic compounds have
giant
what happens to the ions when an ionic compound melts
they are free to move, this allows them to carry electrical charge
what is needed to overcome the ionic bonds to melt solids
a lot of energy
why do ionic solids have high melting points
because alot of energy is needed to break the ionic bonds
why can ionic substances conduct electricity when disolved in water or when molten
because the electrons are free to move
what kind of bonds hold together the atoms in a molecule
strong covalent bonds
why dont molecules carry electricity
because they have no overall charge
why doesnt petrol conduct electricity
because it has no overall charge
why are substances with large molecules more likely to be liquids at room temperature
the forces between molecules, called intermolecular forces, are weak, they overcome when a molecular substance melts or boils, so the substances with smaller molecules will have a low melting point
why do giant covalent structures have high melting points?
because every atom is joined to several other atoms by strons covalent bonds, so it would take an enourmous ammount of energy to break them
give 2 sililarities of graphite and diamond
they are both forms of carbon
they both have covalent bonds
give 2 differences of diamond and graphite
diamond has covalent bonds between laters, graphite doesnt
diamond is transparent, graphite is not
what are fullerines
large molecules formed from large hexagonal rings of carbon atoms, the rings join together to form cage like shapes with different numbers of carbon atoms, some of which are nano sized,
scientists are finding many uses for fullerines eg catalysts, drug delivery into the body and reinforcing metals
why can metals be made into wires
because they are made in layers, this means the atoms can slide over oneanother, they can move into a new position without breaking
give 2 reasons why alloys can be more useful than pure metals
they are harder than pure metals because the different sizes in atoms distort the layers, this means that they are harder than pure metals. Shape memory alloys can have their shape changes and they will bend back into their original shape
why do LD and HD poly(ethene) have different properties
because they are made using different catalysts and different reactions
What are the main differencrs in structures in thermosoftening and thermosetting polymers
Thermosoftening polymers are made up of individual polymer chains that are tangled together. Thermosetting polymers do not melt of soften when you soften them then you heat them
what allows thermosoftening polymers to be remoulded
in thermosoftening polymers the forces between the polymer chains are weak. When they are heated, these weak intermolecular forces are broken and the polymer becomes soft. When the polymer cools down, the intermolecular forces bring the polymer molecules back together so the polymer hardens again
what is a nanoparticle
particles that are a few nanometers in size
how big is a nanometer
one billionth of a meter or 10 to the -9
what is needed before nanoparticles are sold for use eg in deodrants
further research for safety
why do we only count the protons and neutrons to calculate the mass of an atom
because the mass is almost entirely made up of protons and neutrons and electrons make very little difference
what are isotopes
they are atoms of the same element with a different number of neutrons
what is a mole
the relative atomic mass of atoms in the element
how is the reletive atomic mass of a substance found
by adding all the relative atomic masses of the atoms in the formula
how can we calculate the percentage of any of the elements in a compound
divide the reletive atomoc mass of the elelemt by the reletive formula mass of the compound and times it by 100 to convert it as a percentage
what is the empiracle formula
the simplest ratio of atoms or ions in a compound, it is the formula used for ionic compounds
how do you calculate the empiracle formula of a compound from its percentage composition
devide the mass of each element in 100 g of the compound by its A(r) to give the ration of atoms. Then convert this to the simplest whole number ratio
what does the yield of a chemical reaction tell us
how much product is made compared to the maximum ammound that could be made
why is it important to maximuse yield
to conserve earths resources and reduce pollution
what is a reversable reaction
a reaction where the products of the reaction can react to make the original reactions
what do we use paper chromatography to do
detect and identify artificial colours
how do we identify food additives
chemical analysis
