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Chemistry for Engineers
Homework 5
Periodicity
Answer Key
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Hand in by Friday
13 October 13:00
Chemistry for Engineers
Homework 5: Periodicity
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Q1: Which of these lists of elements is in order of increasing electronegativity (i.e. lowest to highest)
a) Mg, Li, I, F, Se
b) Ba, Li, Co, C, Cl
c) Cr, Cu, N, P, Br
d) Cs, Ca, C, Cl, Cu
e) Ni, B, Br, F, N
Q2: Which of these five elements has the greatest (i.e. most exothermic) electron affinity?
a) I
b) S
c) H
d) Cl
e) Mg
Q4: a) For each pair of species, which has the larger radius?
ii) He or Hiv) Fe2+ or Fe3+
Q3: a) For each list, put these elements in order of increasing
electronegativity (i.e. lowest to highest):
i) Sr or Rb
iii) S2- or Cl-
i) N Na Ni
ii) S Se Sr Sn
iii) Cu Ca Cr Cs Cl C
b) Put these elements in order of increasing first ionisation energy
i) Kr Rn Ne
b) For each list, put these elements in order of increasing
atomic radius (size):
i) O C Li Ne
ii) S Te O Se
iii) Ca K Fr Be
ii) I Sb Xe Te
Q6: By considering metallic/non-metallic character
amongst the elements of the following oxides:
i) BeO
ii) NO2 iii) BaO iv) CO2 v) MgO
a) Which oxide is expected to be the most acidic?
b) Which oxide is expected to be is the most basic?
Q5: a) What is the oxidation number of iodine in the following substances?
i) HI ii) KICl4 iii) LiIO iv) HIO3 v) NaIF3
b) What is the oxidation number of sulphur in the following substances?
i) SO2 ii) S8 iii) H2S iv) H2SO3 v) Na2S2O3
c) Which of the above iodine compounds is the best oxidising agent?
d) Which of the above sulphur species is the best reducing agent?
1
Q1: Which of these lists of elements is in order of increasing
electronegativity (i.e. lowest to highest)
a) Mg, Li, I, F, Se
d) Cs, Ca, C, Cl, Cu
b) Ba, Li, Co, C, Cl
e) Ni, B, Br, F, N
c) Cr, Cu, N, P, Br
b)
Q2: Which of these five elements has the greatest (i.e. most
exothermic) electron affinity?
a) I
b) S
c) H
d) Cl
e) Mg
d)
Q3: a) For each list, put these elements in order of increasing
electronegativity (i.e. lowest to highest):
i) N Na Ni
ii) S Se Sr Sn
iii) Cu Ca Cr Cs Cl C
Na < Ni < N
Sr < Sn < Se < S
Cs < Ca < Cr < Cu < C < Cl
b) Put these elements in order of increasing atomic radius (size)
i) O C Li Ne
ii) S Te O Se
iii) K Ca Fr Be
Ne < O < C < Li
O < S < Se < Te
Be < Ca < K < Fr
2
Q4: a) For each pair of species which has the larger radius?
i) Sr or Rb
ii) He or Hiii) S2- or Cliv) Fe2+ or Fe3+
Rb
HS2Fe2+
b) Put these elements in order of increasing first ionisation energy
i) Kr Rn Ne
ii) I Sb Xe Te
Rn < Kr < Ne
Sb < Te < I < Xe
Q5: a) What is the oxidation number of iodine in the following
substances?
i) HI
-1
ii) KICl4 iii) LiIO
+3
+1
iv) HIO3 v) NaIF3
+5
+2
b) What is the oxidation number of sulphur in the following
substances?
i) SO2 ii) S8 iii) H2S iv) H2SO3 v) Na2S2O3
+4
0
-2
+6
+2
c) Which of the above iodine compounds is the best oxidising agent?
HIO3
d) Which of the above sulphur species is the best reducing agent?
H2S
3
Q6: Of the following oxides:
i) BeO
ii) NO2 iii) BaO iv) CO2 v) MgO
a) Which is the most acidic? NO2 N is most non-metal like
b) Which is the most basic?
BaO
Ba has most metallic character
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