OCR Chemistry A-Level - Modules 1-4
exam study guide
Atomic Radius, Nuclear Charge, Electron Shielding - ANS What are the 3 things that affect
first ionisation energy?
Increase. More protons- stronger attraction. Not much extra shielding. - ANS What is the
general trend in ionisation energy across periods? And why?
Decrease due to increased attraction between electrons and nucleus. - ANS What is the
trend in atomic radius across a period?
Increase due to metallic bonds getting stronger. - ANS What is the trend in boiling points
across metals?
Silicon. Strong covalent bonds. - ANS Which element in period 3 has the highest melting
point? And why?
Greater Van der Waals forces. - ANS What do more atoms in a molecule mean for Van der
Waals forces?
The noble gases. They are individual atoms. - ANS Which elements have the lowest
melting and boiling point? And why?
Simple molecular structure. - ANS What bonding structure does phosphorus have?
2+ ions. - ANS What ions do Group 2 elements form?
Increase. The lower the first and second ionisation energies, the more reactive the element. -
ANS What is the trend in reactivity down Group 2? And why?
Decrease. (Increased atomic radius, and the shielding effect) - ANS What is the trend in
ionisation energies down Group 2?
Hydroxides. - ANS What do Group 2 elements produce when they react with water?
green, orange, brown - ANS What are the colours of the halogens chlorine, bromine, and
iodine? in order of question.
Decreases. - ANS What is the trend in reactivity of halogens down the group?
, Oxidising agents. They gain an electron in their outer shell, so they are reduced. This means
that they oxidise other substances. - ANS Are halogens oxidising or reducing agents? And
why?
Add silver nitrate. - ANS Which test can be done to check for halide ions?
Chlorine is white, Bromine is cream, Iodine is yellow. - ANS What are the colours of the
precipitates formed when chlorine, bromine, or iodine is present in the silver nitrate test?
Ag+(aq) + Cl-(aq)= AgCl(s) - ANS What is the ionic equation for the silver nitrate test with
Chlorine? Including state symbols?
2NaOH(aq) + Cl2(aq)= NaClO(aq) + NaCl(aq) + H20(l) - ANS What is the equation to
produce bleach? Including state symbols?
It is 3+ (group 1), 2+ (group 2), 1+ (group 3), -1 (group 5), -2 (group 6), -3 (group7) - ANS
How do you know what oxidation number an element will be at the start of the reaction?
A reaction where an element is simultaneously oxidised and reduced. - ANS What is the
definition of a disproportionation reaction?
Tetrahedral. - ANS What is the molecular shape of NH4+ ?
109.5 - ANS What is the bond angle of a central atom with 4 electron pairs and no lone
pairs, in degrees?
Non-linear, 104.5 - ANS What is the molecular shape and bond angle of H20, in degrees?
2.5 - ANS How much degrees does it go down by each time you add a lone pair to a central
atom with 4 electron pairs?
Octahedral, 90 - ANS What is the molecular shape and bond angles of SF6, in degrees?
Trigonal planar, 120 - ANS If there are 3 electron pairs on the central atom, and no lone
pairs, what is the molecular shape, and bond angle, in degrees?
Delocalised electrons pass kinetic energy to each other. - ANS Why are metals good
thermal conductors?
Because their metallic bonds are too strong to break. - ANS Why are metals insoluble?
Because of the weak forces between layers. - ANS Why does Graphite feel slippery?
Because the covalent bonds are too strong to break. - ANS Why is Graphite insoluble?
exam study guide
Atomic Radius, Nuclear Charge, Electron Shielding - ANS What are the 3 things that affect
first ionisation energy?
Increase. More protons- stronger attraction. Not much extra shielding. - ANS What is the
general trend in ionisation energy across periods? And why?
Decrease due to increased attraction between electrons and nucleus. - ANS What is the
trend in atomic radius across a period?
Increase due to metallic bonds getting stronger. - ANS What is the trend in boiling points
across metals?
Silicon. Strong covalent bonds. - ANS Which element in period 3 has the highest melting
point? And why?
Greater Van der Waals forces. - ANS What do more atoms in a molecule mean for Van der
Waals forces?
The noble gases. They are individual atoms. - ANS Which elements have the lowest
melting and boiling point? And why?
Simple molecular structure. - ANS What bonding structure does phosphorus have?
2+ ions. - ANS What ions do Group 2 elements form?
Increase. The lower the first and second ionisation energies, the more reactive the element. -
ANS What is the trend in reactivity down Group 2? And why?
Decrease. (Increased atomic radius, and the shielding effect) - ANS What is the trend in
ionisation energies down Group 2?
Hydroxides. - ANS What do Group 2 elements produce when they react with water?
green, orange, brown - ANS What are the colours of the halogens chlorine, bromine, and
iodine? in order of question.
Decreases. - ANS What is the trend in reactivity of halogens down the group?
, Oxidising agents. They gain an electron in their outer shell, so they are reduced. This means
that they oxidise other substances. - ANS Are halogens oxidising or reducing agents? And
why?
Add silver nitrate. - ANS Which test can be done to check for halide ions?
Chlorine is white, Bromine is cream, Iodine is yellow. - ANS What are the colours of the
precipitates formed when chlorine, bromine, or iodine is present in the silver nitrate test?
Ag+(aq) + Cl-(aq)= AgCl(s) - ANS What is the ionic equation for the silver nitrate test with
Chlorine? Including state symbols?
2NaOH(aq) + Cl2(aq)= NaClO(aq) + NaCl(aq) + H20(l) - ANS What is the equation to
produce bleach? Including state symbols?
It is 3+ (group 1), 2+ (group 2), 1+ (group 3), -1 (group 5), -2 (group 6), -3 (group7) - ANS
How do you know what oxidation number an element will be at the start of the reaction?
A reaction where an element is simultaneously oxidised and reduced. - ANS What is the
definition of a disproportionation reaction?
Tetrahedral. - ANS What is the molecular shape of NH4+ ?
109.5 - ANS What is the bond angle of a central atom with 4 electron pairs and no lone
pairs, in degrees?
Non-linear, 104.5 - ANS What is the molecular shape and bond angle of H20, in degrees?
2.5 - ANS How much degrees does it go down by each time you add a lone pair to a central
atom with 4 electron pairs?
Octahedral, 90 - ANS What is the molecular shape and bond angles of SF6, in degrees?
Trigonal planar, 120 - ANS If there are 3 electron pairs on the central atom, and no lone
pairs, what is the molecular shape, and bond angle, in degrees?
Delocalised electrons pass kinetic energy to each other. - ANS Why are metals good
thermal conductors?
Because their metallic bonds are too strong to break. - ANS Why are metals insoluble?
Because of the weak forces between layers. - ANS Why does Graphite feel slippery?
Because the covalent bonds are too strong to break. - ANS Why is Graphite insoluble?
