atomic structure and the periodic table Flashcards
number of protons determine what
it determines what the element is
isotopes definition
isotopes are different forms of the same element that have the same number of protons but have a different number of neutrons
equation for relative atomic mass
sum of isotope abundance x isotope mass/sum of abundance of all isotopes
molecules meaning
2 or more atoms held together by chemical bonds
compound meaning
2 or more different elements that are held together by chemical bonds
mixture meaning
two or more substances not chemically bonded together
what can mixtures be separated by
by physical processes such as filtration crystallisation simple distillation fractional distillation and chromatography these are physical processes and do not involve chemical reactions and no nee substances are made
what is filtration
separating insoluble solids from liquids
process of filtration
using filter paper and a funnel to filter the insoluble solid from the liquid
process of evaporation
place solution in evaporating dish and heat with a bunsen burner while a tripod is separating it this will cause solvent to evaporate, crystals will start to form.
solvent will disappear leaving dry crystals as our solid
what is thermal decomposition
some solids decomposing when heated
process of crystallisation
solution placed in evaporation dish dish placed in a water bath. bunsen burner is heating the solvent. once crystals start to form we turn off bunsen burner and leave it to cool. as solution cools more crystals will form as solids are less soluble at cooler temps. next filter out the crystals from the solution using filter paper and funnel. then dry crystals.
what is simple distillation
separating out a liquid from a solution
process for simple distillation
have solution in a flask and have a bung seal the flask so no gas can escape. place thermometer through bung to measure temp. next condenser is connected to flask which has a continuous stream of cold water. with water being fed into water jacket at the bottom and coming out at the top. end of condenser have a beaker to capture pure liquid. finally heat flask with bunsen burner.
what does the water jacket do on a condenser for simple distillation
it cools the vapour to a liquid
what is fractional distillation
main technique for separating mixtures of liquids
process for fractional distillation
flask with a bung. attached to a fractionating column which is attached to a condenser and at the end of the condenser is the beaker for the pure substance
what is a fractionating column
it is full of little glass rods and is cooler at the top than at bottom.
the glass rods are used to condense the liquids which are not intended to be removed yet back into the flask.
the plum pudding model and the differences between plum pudding model and nuclear model
the plum pudding model was discovered by jj thompson
it suggested that the atom is a ball of positive charge either negative electrons embedded in it.
nuclear model proposes the idea that there is a nucleus containing protons with electrons orbiting the nucleus in a cloud
scattering experiment with sheet of gold
they shot alpha particles at the sheet of gold and some of the alpha particles either went through or they deflected away to the side . this proved jj theory wrong. rutherford proposed the idea of a nucleus and it contained the positive charge and the negative charge surrounding the nucleus.
how to find number of protons and electrons on the periodic table
look at atomic number
which group has a full outer shell on periodic table
group 0 the noble gases
what did mendeleev do
he devised the periodic table and predicted new elements we hadn’t discovered yet.
what is the group 7 elements called and how does there reacivity work
they get less reactive down the group and are called the halogens
group 1 elements are called what and how does there reactivity work
they are called alkali metals and they get more reactive as you go down the group
are metals positive or negative when they are ions
they form positive ions
do metals lose or gain electrons
metals always lose electrons non metals gain electrons
properties of metals and non metals
metals
mettalic bonding
malleable
conducters
high mp and bp
non metals
lower densities
low mp and bp
bad conducters
brittle
dull in colour
properties of transition metals
can form more than one ion
they make very good catalysts
properties of alkali metals (group 1 metas)
soft
low density
low mp
they are much more reactive and react vigorously with water
down the group they are more reactive
mp and bp decrease down the group
properties of halogens
they exist as diatomic molecules (2 atoms)
which is a covalent bond
mp and bp decrease down the group
reactivity decreases down the group
when halogens react with metals they always end in identical e.g. fluoride
displacement reactions
more reactive halogen will always displace less reactive ones
group 0 properties
they are inert (dont react with other elements)
they are a colourless gas
they exist as single atoms
they are non flammable
there bp increases as you go down the group
