ATOMIC STRUCTURE AND PERIODIC TABLE - need to do nuclear model onwards Flashcards
an element-
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-how many are there-
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an atom is-
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compound-
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-properties of compounds compared with of its elements
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-how to separate a compound
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mixture-
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-how to separate a mixture
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-what happens to properties of each substance in a mixture
molecule-
-element consists of atoms with same atomic number- all the same atoms
-about 100
-the smallest part of an element that can exist
-compound- 2 + different elements chemically combined in a fixed proportion
-compounds usually have totally different properties to the elements they’re made from
-only separated into elements by chemical reactions
-2+ different elements / compounds not chemically combined
-separated by physical processes
-unchanged
-molecule- any element chemically combined eg o2
-chemical reactions involve….
-physical process to separate a mixture x 5
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-do they involve chemical reactions
-are new substances made
formation of one or more new substances and often a detectable energy change
-filtration-insoluble solid from liquid
-crystalisation-soluble salt from liquid
-simple distillation-soluble solid + liquid
-fractional distilation-2 liquids w/ missible b.p’s
-chromotography
NO
how to do a filtration- 4 steps
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-crytalisation / evaporation done if….
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-evaporation done if-
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.how to do crystalisation
4 steps.
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-how to do evaporation-
3 steps
-filter paper folded cone shape- put in funnel
-pour mixture
-liquid and any dissolved substance passes through
-insoluble solid left
-the salt is aqueous-can be dissolved
-salt doesn’t decompose when heated
-pour solution in evaporating dish
-gently heat- solvent evaporates, solution becomes concentrated
-when some solvent evaporates/crystals start forming, remove dish from heat, let solution cool
-filter the crystals and leave them in warm place to dry/ drying oven/ desiccator/pat dry w/ filter paper
-pour solution in evaporating dish
-heat solution gently , solvent evaporates, solution becomes concentrated
-keep heating till left w/ dry crystals
-pro of evaporation
-what can you use to heat the solution
-how does the state symbol of the salt change after crystallisation/ evaporation
-quicker than crystalisation.
-bunsen burner- water bath- electric heater
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-goes from (aq) to (s) as its no longer dissolved in liquid
simple distillation used to separate…
simple distillation steps x5
liquid from solution if we want the liquid
-heat solution to evaporate liquid
-vapour runs through tube surrounded by condenser
-cold water running through condenser
-vapour cooled and condenses and collected in beaker
-rest of solution left in flask- may be as crystals
what happens when seawater undergoes simple distillation
-why isn’t distillation used to get drinking water
-problem with distillation
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-water evaporates and condenses- we get pure water
-salt left in flask
-alot of energy needed for simple distillation
-only use it to separate things with very different boiling points, if temp goes higher than b.p of substance w/ higher bp, they will mix again
what is fractional distillation used
-what is the set up for fractional distillation
-why is this important
mixture of liquids with miscible b.p’s (close but different)
-flask containing mixture connected to fractionating column (long column w/ hundreds of glass rods)
-cooler at top
-glass rods- high s.a
process of fractional distillation
#1- lowest bp liquid
#2-mid bp liquid
#3- highesr bp liquid
-heat to bp of #1
-#1 and some #2 and #3 will evaporate
-#1 vapour passes into condenser- condenses into beaker
- as #2 and #3 go up column its cooler. they come in contact w/ glass rods that are cooler than their bp
- #2 and #3 condense
-repeat, heat to bp of #2
-#2 condenses into empty beaker
-now can assume only thing left in flask is #3
-or heat to bp of #3 and let it condense into empty beaker
Chromatography used to separate….
-process - 6 steps
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.why do you see different spots
separate substances based on different solubilities
-draw pencil line on chromatography paper - near bottom
-put dot of first colour on pencil line and dot of second next
-place bottom of paper in solvent- make sure solvent doesn’t touch ink
-put lid on to stop solvent evaporating
-solvent makes its way up paper dissolves ink in coloured dots
-ink is carried up paper as well
-when solvent front is at almost at top of paper, remove paper+ let dry
-each dye in ink will move at different rate- dyes will separate out- each dye will form spot in 1 place
why do we draw starting line in pencil
-why should ink spot not touch solvent
pencil marks are insoluble- won’t dissolve in solvent
-don’t want spot to dissolve into solvent
what solvents can be used
Rf value =
depends on what’s being tested- some compounds dissolve well in water-
other solvents- eg ethanol - may be needed
-distance moved by substance / distance moved by solvent
no unit…
-what is the solvent front
-how do you measure distance moved by chemical
-point the solvent has reached up the paper
-from pencil line to centre of spot
what is the stationary phase
what is mobile phase
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how to tell if a colour is pure
how to tell if a colour is a mixture
the paper, it does not move
solvent is the mobile phase as it moves
- (a pure compound) will produce a single spot in all solvents
-compounds in a mixture may separate into different spots depending on the solvent used
why does paper chromatography work
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how to identify an unknown substance
different substances have different solubilities . A more soluble substance travels further up the paper than a substance that is less soluble. That way we can seperate substances based on solubility
-workout Rf value and compare to datatbase
if 1+ substances have this Rf value than compare it in other solvents
(if substance never analysed bfor, rf value x be on database)
-if any dyes in the ink are insoluble in the solvent they will….
-what would happen if you used pen to draw starting line
they’ll stay on the baseline
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-components in ink will separate out along with substance your analysing
-before electron discovered, ppl thought atoms were
-whose model was this
-tiny spheres that couldn’t be divided into smaller parts
-Dalton model
plum puddding model suggests the atom is
-why was this model made
sphere of positive charge with negative electrons embedded in it
-electrons were discovered
ALPHA SCATTERING EXPERIMENT
what did Rutherford and Marsden expect to happen
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-what did they do
-what happened
-expected particles to pass through or slightly deflected- +ve charge of atom counteracted by -ve electrons so overall neutral charge of atom
-fired +ve charged alpha particles (tiny particles) at thin sheet of gold foil
-most passed straight through
-some deflected
-some bounced/ deflected backwards
results from scattering experiment led to conclusion that-
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how did they come to this conclusion
mass of atom concentrated at centre- nucleus- and the nucleus was charged
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-most went straight through, so atom is mostly empty space
-some deflected- alpha particles with + charge repelled by concentrated + charge of nucleus
-some bounced back, directly striked the nucleus- centre of atom has a lot of mass
the alpha scattering experiment led to which model- describe it
-the nuclear model
most of atom empty
-positive nucleus at centre-mass of atom
-negative electrons around edge
who adjusted the nuclear model
-how
-why was it accespted
niels bohr
suggests electrons orbit the nucleus at specific distances (now energy levels)
-theoretical calculations agreed with others experimental observations
After Bohr found energy levels, what was the next finding that changed the nuclear model
The positive charge of any nucleus can be subdivided into a whole number of smaller particles.
Each particle has the same amount of +ve charge (as a hydrogen nucleus)
These particles named: proton.
-Bohr added energy shells
-then protons were added
-who added the next thing to the nuclear model
-how long after ……… did he discover this
James chadwick
provided evidence of neutral particles in the nucleus
-20 years aster the nucleus became an accepted scientific idea
radius of an atom
radius of nucleus
0.1 nm (1x10 ^ -10 m)
1/10 000 of the atom (1x10^ -14)
