Flashcards
section 2 - mel russels - revision notes
Cards in this deck (69)
- 1oxidising ability1)reaction between 1 halogen & ion of another halogen
2)eg chlorine and iodine
3)iodine loses e - iodine molecules
chlorine gaine e -chloride ions
4)redox reaction - 2fluorine1)oxidising agent
2)very strong - 3Bond enthalpies1)heat needed to break 1 mole of covalent bond to produce individual atoms
2)starting from gas to gaseous atom - 4Trends in electronegativity1)electronegativity: a measure of the tendency of an atom to attract binding pair of electrons
2)measured on Pauling scale
3)fluorine most electronegative element
4)electronegativity decreased down a group - 5trends in atomic radius1)Atomic radius increases down group
2)no. of layers in inner electron increases - 6whats electronegativity?relative tendency of bonded atom to attract electrons itself
- 7what happens if 2 atoms of equal electronegativity bond together, Cl2?1)atoms equal electronegativity, both have the same tendency to attract bonding pair of electrons so will be found to average halfway between 2 atoms
- 8whats a covalent bond?a bond where electrons are shared evenly between 2 atoms - attraction that holds molecule together
- 9whats a polar bond?a covalent bond in which there's a separation of charge between one and the other
- 10what happens if one atom is a lot more electronegative than the other when covalently bonded?more electronegative atom attracts electron pair (greater share of e density -) more than the other (+)
- 11what happens if one atom is a lot more electronegative than the other is bonded together?electron pair attracted to more electronegative atom.
less electronegative atom has lost attraction for the bonding pair of electrons (loses e) resulting in formation of ions - 12the attraction that a bonding pair of electrons feel for a particular nucleus depends on what factor?distance from bonding pair of 2 nuclei, no. of protons in the nucleus, atomic radius (size of an atom), no. of energy level
- 13why does electronegativity decrease as you go down the group in the periodic table?electronegativity decreases because bonding pair of the electron increases the distance from the attraction of nucleus (further away, less able to attract electrons)
- 14what determines the size of elements?1)no. of layers of e around the nucleus
2)pull the outer e feel from the nucleus - 15why is Cl bigger than F?more inner layers of e
- 16why has f got smaller electron affinity than Cl?1)incoming e repulsed from densely packed existing electrons, offsets some of the attraction between the nucleus
2)offset causes repulsion, lowers electron affinity of F atom below Cl - 17why does 1 have the smallest electron affinity of the group?I is largest of halogens and incoming electrons are further away from nucleus so feels less attraction by it.smaller attraction between incoming e and nucleus, smaller effinty
- 18definition of enthalpy?the heat required to break 1 mole of a covalent bond to produce individual atoms, starting with original substance in gaseous state & ending with a gaseous state
- 19why is F the most electronegative of these elements?the small size off atom pull from f atom nucleus is very strong. the larger size of another atom, smaller effect of nucleus
- 20definition of eletron affinity?first electron affinity is the energy released when 1 mole of a gaseous atom requires e to form 1 mole of gaseous ions
- 21define oxidation in terms of electron transfer?oxidation is loss of electrons
- 22define reduction in terms of electron transfer?the reduction is the gain of electrons
- 23whats oxidising agent?causes something else to be oxidised (loses e) takes e for itself and gets reduces (gains e)
- 24whats reducing agent?causes something else to reduce (gain e) gives own e for itself so gets oxidised
- 25whats a co-ordinate bond?where bonding e pair come from same species. (diff to covalent bond where e comes from different species)
- 26what's the definition of a strong acid?a strong acid is one that fully dissociates in solution
- 27what's the definition of a weak acid?doesn't fully dissociate in solution
- 28what's the definition of acid?acid is a proton H+ donor
- 29explain why hydrogen bromide & hydrogen iodide cant be prepared using sulphuric acid?sulphuric acid is a strong oxidising agent, therefore halide ions would also be oxidised
- 30write equation between hydrogen chloride and water?1)iodine ions are oxidised as they have lost their electronic charge to form iodine
2)bromine is reduced, gains e charge from bromide ions
3)bromine acting oxidising agent as it causes iodine to lose e and form iodine - 31why does hydrogen fluoride have higher Bp than any other?the bond between hydrogen and fluoride is polar, requires less energy to break.as results of bonding each fluoride has 3 lone pairs of e which participate in bonding to the hydrogen of second HF molecule
- 32why does oxidising ability decease from chlorine to bromine iodine?down the group, ions less attractive to water molecules as they get bigger. The ease toms attract electrons matters, cuz important as hydration enthalpy of - ions formed.
- 33whys fluorine such a powerful oxidising agent?atomisation energy of fluorine is low.reflects low bond enthalpy of fluorine.high hydration enthalpy of fluoride ion.ions very small. stronger the attraction, more heat evolved why hydrated ions are formed
- 34the trend in atomic radius?1)increases down the group
2)radius of atoms governed by...
-no. of layers of e around the nucleus
-pull outer electrons free from the nucleus
3)no. of electrons increases down the group. more layers of e, more space occupy. electrons repel each other.atom bound together get bigger down the group - 35definition oxidationloss of electrons
- 36definition of reductiongain of electrons
- 37definition of oxiding agentoxidises something else
- 38OIL RIGO -oxidation
I - is
L - Loss
R - Reduction
I - IS
G- Gain
the oxidising agent takes e from other substances, an oxidising agent must gain e, because reduces and reducing agents must lose e to become oxidised - 39state and explain the trend in the oxidising ability of halogens?1)when halogens involved in oxidising agent, halogens end up as halides with water molecules attached to them.
2)down group, ease of hydrated ions formed falls, so hydrogen bonds less effective as oxidising agents(less able to attract/take e from something else) - 40why does F2 have a weak single bond, compared to CL2bonding e are attracted to both nuclei.small size offer lone pair, repulsion and tend to counteract attraction between bonding pair and 2 nuclei
- 41state trend/chemical formula of each halide? explain why the trend is regular1)HF,HCL,HBr,Hi
2)no lone pair on H atom, the repulsion between lone pairs od bonding electrons is present.
size is the main factor
bigger the halogen, further bonding pair is way from nucleus - 42Atomisation energythe energy needed to produce 1-mole of isolated gaseous atoms starting from element in the standard state.
- 43hydration enthalpy1)energy released when 1 mole of gaseous ions dissolve in water to produce hydrated ions
2)fluorine produces a lot of heat - 44fluorine as an oxidising agent1)low atomisation energy
2)low bond enthalpy
3)very high hydration enthalpy
4)hydrated enthalpy changes down a group, ions become less attractive to water molecules - 45chlorine, bromine and iodine1)halogens increase in the group, oxidised ions of one lower down
2)chlorine can oxidise bromide ions
3)chlorine only oxidises iodide ions
4)bromine can easily oxidise iodide ions. iodine won't oxidise any other halide ion - 46bond enthalpy in halogens1)covalent bond:
bonding pair attracted to both nuclei
2)atoms get bigger, bonding pair further from nuclei, the strength of bond decreases
3)bond enthalpies of CL-CL,Br-Br, I-I bond decreases
4)F-F bond is an exception, lone pairs of 2 atoms get close together, repulsion
5)weakens the bond
6)halogens atoms attach to hydrogen atom
7)no lone pairs of the hydrogen atom
8)halogen gets bigger, bonding pair more distant from nuclei
9)attraction is less
10)bond gets weaker
11)bond enthalpy decreases down the group - 47trends in melting and boiling point1)both increase down the group
2)F & CL are gasses at r.t
3)Br is liquid at r.t
4)l is solid at r.t
5)molecules increase, intermolecular attraction gets stronger
6)more energy needed to boil/melt - 48the trend in first electron affinity1)energy released when 1-mole gaseous atom each acquiree to form 1 mole of gaseous ions
2)down(less heat is given out) group
3)fluorine is an exception
4)f is a very small atom
5)measure of attraction between incoming e and nucleus
6)incoming e close to the nucleus
7)enters region of - charge
8)repulsion, lessens the attraction
9)electron affinity lower than Cl - 49trend in electronegativity1)measure of the ability of an atom to attract bonding pair of e towards itself in a covalent bond.equal sharing of e
2)most electronegative is fluorine
3)en decreases down group, atom less able to attract bonding pairs of e
4)as halogens increase, bonding pair further away from halogen nucleus(e layers increase) so less attraction towards it.down group decreases electronegative - 50The trend in electron affinity1)decreases down group, e affinities decreases(less heat)
2)energy released when 1 mole of gaseous atoms each acquire an e from one mole of gaseous
3)ef=measure of attraction between incoming electron and nucleus.increase attraction and electron affinity.atoms get bigger,e further from the nucleus, less attraction.electron affinity decreases down group - 51whys electron affinity important?many elements exist as anions naturally in compounds.
- 52electronegativity pattern?decreases down the group and decreases oxidising ability down the group
- 53elements on the right side of the periodic table?more energy-efficient in gaining electrons to complete valence shells.shells half full so easier to pull electrons into the shell to form anions.rather than donate one
- 54general reactivity of group 17 elementsdecreases down, group.
Atomic radius increases.
increase of electronic levels
decreases attraction of valence e of other atoms - 55small atomsincreases ionization energy.lots of energy to remove e from a small atom cuz of strong attraction to nucleus
- 56octet rulethe tendency of an atom to prefer to have 8 electrons in the valence shell
- 57ionisation energy1)energy required to remove outermost e from atom
2)important because elements exist as cations naturally in compounds - 58fluorinesmall atom, the electron density is high causing repulsion, decreases attraction from the nucleus to decrease electron affinity to below chlorine
- 59electron affinitythe energy change when one electron is added to atom per mole
- 60trends in melting and boiling points1)both increase down the group
2)molecules get bigger, decrease down group, more electrons, creating attraction
3)attraction increases. more heat energy is supplied to turn them into liquid/gas so mp and bp increases - 61the trend in bond enthalpies (bond energies/strength)1)bond enthalpy is the heat needed to break one mole of a covalent bond to produce individual atoms, starting from gas gate to gaseous atoms
2)size of attraction depends on distance of 2 nuclei
3)atoms get bigger, bonding pair further from nuclei, the strength of bond falls
4)f2 not trend cuz covalent bond is weak. atoms smaller(bond shorter) lone pairs (non-binding) close together to experience repulsion, weakens bonds - 62what happens when halogens attached to a hydrogen atomhalogen atom increases, bonding pair more distance from nucleus.attraction is less, gets weaker, bond enthalpy falls
- 63oxidation ability of group 7 elements (halogens)1)oxidation - loss of electrons
2)elements take E to make ions
3)all elements potentially oxidising agents
4)fluorine - powerful oxidising agent
5)chlorine can take e from bromide/iodide ions
6)bromide/iodine cant get back e from chloride ion formed
7)chlorine,more powerful oxidising agent than bromine & iodine
8)bromine, more powerful oxidising agent than iodine.bromine can remove e from iodide to give iodine.
9)oxidising ability decreases down group - 64atomisation energythe energy needed to produce 1 mole of isolated gaseous atoms starting from an element in standard state
- 65electron affinitythe energy released when 1-mole gaseous atom acquire an e from 1 mole gaseous 1-ions
- 66hydration enthalpythe energy released when 1 mole of gaseous ion dissolves in water to produce hydrated ions
- 67why is fluorine a stronger oxidising agent than chlorine?1)atomisation energy off is low (low bond strength)
2)hydration enthalpy - increase cuz ion is small. the strong attraction between F and H2o molecule. stronger attraction, more heats evolved when hydrated ions are formed
3)down group, decrease attraction to H2O molecules, they get bigger
4)reducing the ability of halide ions, decreases down the group - 68The acidity of hydrogen halides1)Colourless gasses at room temp
2)produces steam at r.t
3)hydrogen fluoride, increases bp for the size of the molecule, cuz forms hydrogen bonds. other halides don't.
4)more hydrogen halides by the reaction of ionic halide on an acid
5)HF is a weak acid - 69why is HF a weak acid?1)strong H bond between un-ionised HF & water. costs a lot to break, don't occur in hydrogen halides
2)large decrease in entropy when HF reacts with water.attractiveness is small F- ions produced impulses a lot of order in surrounding water molecules nearby. Effect falls when halide ions get bigger
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- Flashcards on section 2 - mel russels - revision notes, created by Aarden Tidbury on 04/01/2020.
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