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)
what is atomic mass
what is atomic number
no. of protons + neutrons
-at the top
-the larger number
number of protons
-smaller number
-also the number of electrons
what are isotopes
atom w/ different neutron number
where are metals and non metals found in table
-how are elements arranged-why
-metals left and bottom & non metals right and top
-according to atomic (proton) number
SO elements w/ similar properties are in same groups/column
-Why is the table called the periodic table
-why do elements in a group react in similar way
similar properties occur at regular intervals
-same no. of outer electrons so similar chemical properties
what were dobereiners triads
elements w/ similar properties occured in threes
-newland organised according to atomic mass
what did madeleev do
arranged all elements in order of increasing atomic weight
-switched order of some elements so they fitted patterns of other elements in same group
-left gaps for undiscovered elements
-How were elements ordered bfore discovery of pro,neut, elec
-what was the problem
-order of atomic weight(mass)
-incomplete
-elements placed in inappropriate groups if strict order of atomic weight not followed
why did ppl accept madeleev’s table
elements w/ properties predicted were found
how are elements arranged now
-why
-order of atomic number-proton no.
(proton X discovered in mandeleevs time so ordered by atomic weight)
-atomic no. never changes bcse proton no. never changes
-atomic weight can change due to isotopes, so elements can appear in wrong order
difference btwn currentt able + old/madeleevs one
-has group 0 (not all discovered bfor)
-ordered by atomic no.
GROUP 0
-how reactive-why
-how many outer electrons
-monatomic OR diatomic
-unreactive- not easily form molecules AS…
-atoms have stable arrangement of electrons
-all Xept helium have 8 electrons in outer shell
-helium has 2
-monotomic- not bonded to eachother
GROUP 0
-what happens down group
-what state are they at room temp
-are they flammable
-boiling point increases down group - as relative atomic mass increases
-colourless gas
-inert so non-flammable
GROUP 0
why does boiling point increase with increasing relative atomic mass
-more electrons in each atom
-greater intermolcecular forces between molecules
-need more energy to overcome
METALS-
-2 categories
-prperties of alkali’s are due to
grp 1 and 2- highly reactive
- transition metal- less reactive
-the single outer electron
-reactions of
lithium
sodium
potassium
with oxygen
with chlorine
with water
WITH OXYGEN- REACT RAPIDLY
lithium + oxygen = Li2O (oxide)
sodium + oxygen= Na2O (oxide) + Na2O2 (sodium peroxide)
potassium + oxygen= K2O2 (peroxide) + KO2 (superoxide)
alkali + oxygen = alkali oxide
2 Li+Cl2=2 LiCl
2 Na+Cl2=2 NaCl
2 K+Cl2=2 KCl
alkali +chlorine= alkali chloride (salt)
REACT RAPIDLY W/ CHLORINE
alkali metals and water
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-why does universal indicator turn purple
-why is there effervescence
2 Li + 2 H2O = 2 LiOH + H2
2Na+2H2O→2NaOH+H2
2K(s)+2H2O(l)→2KOH (aq)+H2(g)
metal + water= metal hydroxide (salt) + hydrogen
reactions more rapid down group
li- reacts rapidly, fizzing/effervescence, universal indicator goes purple
Na- more rapid reaction, gas produced, water turns alkaline
K- extremely rapid, gas produced, water turns alkaline
-the metal hydroxide made in ALKALI
-hydrogen gas produced
properties of all group 1 alkali’s
-what happens to reactivity down group
soft
low density (first three less dense than water)
-get larger down
-force of attraction btwn nucleus + electron decreases
AS is more distance btwn them
-outer electron shielded from nucleus by more internal levels
-easier to be lost
(b.p and m.p decrease down grp)
ALKALI METALS only ever form ionic compounds. These are…
usually white solids, dissolve to form colourless solutions
alkali + water= alkali hydroxide + hydrogen
-what happens to the energy released by the reaction down the group
-increases down group
GROUP 7
-what are they called
-metal or non metal
-diatomic/monotomic
-what is room temp
-what happens to b.p and m.p down group
-what happens to relative molecular mass down group
-what happens to reactivity down group
-halogens
-non metal
-diotomic
-20 *
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-increase down group.
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-increases down group- molecules get bigger
-reactivity decreases
GROUP 7 HALOGENS
-when they react with other non metal atoms what is formed
-when they react with metal atoms what is formed
-covalent compounds- eg HCl (share electrons)
-ionic compounds-
form 1- ions- halides eg fluoride/chloride
-what happens to reactivity down the HALOGENS - grp 7
-why
-reactivity decreases down grp
greater distance btwn outer shell and nucleus
outer shell shielded from nucleus by more shells
so less force of attraction between outer shell and nucleus
so harder to attract more electrons
a more reactive halogen can …….. a less reactive halogen in …..
A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salts
a more reactive halogen replaces the salt of the less reactive halogen from the aqueous solution of its salt- (the og salt dissolved in water)
chlorine + potassium iodide → potassium chloride + iodine
Cl2(aq) + 2KI(aq) → 2KCl(aq) + I2(aq)
Compare properties of group 1 alkali metals and transition metals
7 points
ALKALI’S:
soft
lowish melting points
low density
react rapidly
form +1 ion
TRANSITION METALS:
hard/strong
high melting point
high density
less reactive
form ions with different charges
-coloured compounds
-used as catalysts
-good conductors
(shiny)
example of transition metals being used as catalysts x2
nickel based catalyst used in hydrogenation of aljenes
iron catalyst used in haber process
5 main properties of alkali metals
soft
low melting point
low density
react rapidly
form +1 ion
properties of metals
x4
-why do metals share similar properties
strong hard to break
malleable- can be bent/hammered
good conductors
high m.p and b.p
-they all have metallic bonding- causes similar physical properties
properties of non metals x5
-why are they different to properties of metals
dull
brittle
not always solid at room temp
don’t conduct
-lower density than metals
-don’t have metallic bonding
how does electronic structure of metals affect how they will react/chemical properties
metals to left
-don’t have many outer electrons to lose
metals to the bottom
-electrons far from nucleus- easy to lose
SO feasible to lose electrons to become stable w/ full outer shell
why are the chemical properties of non metals different to metals- talk about bonding
forming +ve ions is hard
non metals to right
-would need to lose many outer electrons
metals to the top
-electrons close to nucleus, easy to gain electrons
SO feasible to gain electrons/share to become stable
