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38 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Proton mass ?charge ? Neutron mass ? charge ? Electron mass ? Charge ? |
Proton mass 1 charge +1Neutron mass 1 charge 0Electron mass 1/200 -1 |
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Mass number? Atomic (proton) number? |
Mass number = total number of protons and neutrons Atomic (proton) number = the no. Of protons in the nucleus. It identifies the element |
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Define Relative atomic mass Ar |
The average mass of an atom of an element on a scale where an atom of carbon-12 is 12 |
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What are Isotopes? |
Isotopes are atoms with the same number of protons but different number of nuetrons |
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Explain why isotopes generally have the same chemical properties? |
They have the same electron configuration and its the electron configuration that determines how they react so they have the same chemical properties. |
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Why do isotopes of an element have diffferent physical properties? E.g densities Diffusion rates |
Because physical properties depend more on the mass of an element and isotopes have different masses. |
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Relative isotopic mass |
The mass on an atom of an isotope of an element on a scale where an atom of carbon-12 is 12 |
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Relative molecular mass |
The average mass of a molecule or formula unit on a scale where an atom of carbon 12 is 12 |
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Tof 1 vacuum |
Whole apparatus kept under a high vacuum to prevent the ions that are produced from colliding with molecules from the air |
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2 Ionisation (electrospray) |
- sample dissolved in volatile solvent then forced through fine needle connected to positive high voltage supply -this produces tiny positively charged droplets which have lost electrons to the positive charge of the supply. -the solvent evaporates from the droplets into the vacuum and the droplets get smaller and smaller untill they contain no more than a single positively charged ion. |
3 points |
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3 Acceleration |
- positive ions are accelerated by an electric field to towards a negatively charged plate. ( so that they all have the same kinetic energy) - lighter ions and more highly charged ions achieve a higher speed |
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4 Ion drift |
The positive ions travel through a hole in the negatively charged plate forming a beam and travel along a tube.
Through this tube velocity is constant |
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5 detection |
- when ions with the same charge arrive at the detector, the lighter ones are first as they have higher velocities. - they are discharged by gaining an electron from the plate which completes the circuit - so a current is generated which can be measured to determine the no. of ions hitting the plate and their flight time is also recorded DATA ANALYSIS- signal passes to computer and generates mass spec |
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Relative atomic mass calculation |
Times each peak mass/charge by its percentage Add up each total Then divide by 100 (or the total abundance) |
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Orbitals top tips |
-4s sub shell fills up first Electrons fill orbitals singly before they start sharing. - why? Because two electrons in the same sam orbital must have opposite spins even still they repel eachother so its better to fill up singly first |
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The first ionisation energy |
The energy needed to remove one electron from one mole of gaseous atom to form one mole of gaseous ions with a charge of +1 O (g) >>> O+ (g) + e- |
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Factors affecting ionisation energy |
Nuclear charge - more protons = higher positive charge in nucleus = stronger attraction for electrons. Distance - an electron close to the nucleus is much more strongly attracted to the nucleus than one far away Sheilding - this when a increase in inner electrons between the outer electrons and nucleus causes a decrease in the attraction between outer electrons and the nucleus. |
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Across a period ionisation energy increases despite increase in electrons why? |
- This is because the number of protons increases so theres a stronger nuclear attraction. - Despite the increase of electrons theres no extra sheilding because the extra electrons are at roughly the same energy level.
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Why is there a drop between groups 2 and 3 ionisation energy across the period? |
Eg Mg and Al Al is in a 3p orbital not 3s. 3p orbital has a slightly higher energy than 3s orbital so the electron is on average found further away from the nucleus. Also the 3p orbital has additional sheilding provided by the 3s2 electrons. Both these factors together are strong enough to override the effect of increased nuclear charge, resulting in ionisation energy dropping slightly |
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Ionisation energy decreases down group 2 |
As you go down the group the no. of inner shells increases so theres an increase in sheilding so the attraction between the outer electrons and nucleus less. So outer electrons are easier to remove. |
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Why is there a drop between groups 5 and 6 ionisation energy across the period? |
Eg phosphurous and sulfur The shielding is identical for both atoms and the elctron is removed from an identical orbital. But in phosphorus the electron is being removed from a singly occupied orbital instead of an orbital containing two electrons like sulfur. Its easier to remove an electron from an orbital with two electrons due to repulsion between them so the ionisation energy drops for sulfur. |
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Second ionisation energy trend? |
Second ionisation energies are greater than the first ionisation energies because the electron is being removed from positive ion wich will require more energy. |
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Orbitals trasition metals behave badly Cr (chromium) and Cu (copper) |
They donate one of the 4s elctrons to the 3d sub-shell because they're happier with a more stable full or half full d sub shell. Cr = [Argon] 3d5 4s1 Cu =[Argon] 3d10 4s1 |
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Transition metals behave badly when they become ions. How? |
They loose their 4s electrons before their 3d electrons Fe: 3d6 4s2 >>>> Fe 3+ : 3d5 |
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The mole |
- One mole 6.02 x 10^23 particles - Number of particles = number of moles x Avogadros constant - number of moles = mass of substance / Mr - moles = (conc x vol(cmcubed))/1000 - moles = concentration x vol (dm^3) |
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Neutralisation rection |
When an acid reacts with an alkali to make salt and water |
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Empirical formula |
Find the moles of each element then divide each mole value by the smallest mole value you found this will give you the empircal ration thus formula |
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Calculating theoretical yeild |
-Work out moles of the reactant m/mr - use mole ratio from equation to find moles of the product - Now find the Mr of the product - theoretical yeild = no. Moles x mr - |
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Actual yeild is always less than theoretical why? |
-Sometimes not all starting chemicals react fully - some solution gets left on filter paper - lost during transfers between containers - or it forms other unuseful products |
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Percentage yeild formula |
Percentage yeild = actual yeild/ theoretical yeild × 100 |
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Standard solution |
Any solution that you know the exact concentration of. |
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Ideal gas equation |
pV = nRT P - Pa V - m^3 n - no. of moles R - 8.31 T - (K) C to K = +273 |
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Atom economy |
Its a measure of the proportion reactant atoms that become part of the desired product (rather than by-products) in the balanced chemical equation. |
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Why is atom economy better than percentage yeild? |
Percentage yeild doesnt measure how wasteful a reaction is as the % yeild could be high but still be wasteful if a lot of atoms from the reactants are used to make by products rather than the desired product |
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% atom economy formula |
(Molecular mass of desired product/sum of molecular masses of all reactants ) x100 |
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Environmental advantages |
-Many raw materials are in limited supply so it their used effiently in processes with high atom economy its more sustainable. -waste chemicals can be harmful to the environment so less is more |
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Advantages of high atom economy |
-Its more efficient because a reaction with high atom economy will need fewer raw materials to create the same amount of desired product than a reaction with a lower atom economy . - the company will also have less waste to deal with so less money is spent separating desired products from waste products. Plus any waste products will have to be disposed of safely, which increases costs further |
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Making standard solution E.g 2.00mol/dm3 in 250cm3 |
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