Question Bank (Solutions): Classification of Elements & Periodicity in Properties | Chemistry Class 11 - NEET PDF Download

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1. (d) : Unnilunium – Mendelevium ? (a)-(i) 
Unniltrium – Lawrencium ? (b)-(ii) 
Unnilhexium – Seaborgium ? (c)-(iii) 
Unununnium – Roentgenium ? (d) (iv) 
2. (a) : The electronic configuration of the element 
with Z = 114 (Flerovium) is [Rn]5f
14 
6d
10
7s
2
7p
2
. 
Hence, it belongs to carbon family which has the same 
outer electronic configuration. 
3. (a) : The   electronic   configuration   of    an    atom: 
1s
2 
2s
2 
2p
6 
3s
2 
3p
6 
3d
3 
4s
2
 
In the configuration, the last electron of the atom is 
filled in d-subshell as 3d
3
. Thus, this element belongs to 
d-block of the periodic table with group no. VB or 5. 
4. (c) : Atomic number of the given element is 15 and 
it belongs to group 15. Therefore atomic number of the 
element below the above element = 15 + 18 = 33. 
5. (c) : Electronic configuration of an element with 
Z = 33 is 1s
2
2s
2
2p
6
3s
2
3p
6
3d
10
4s
2
4p
3
. 
Hence, it lies in VA or 15
th 
group. 
6. (c) : Elements (a), (b) and (d) belong to the same 
group since each one of them has two electrons in valence 
shell. In contrast, element (c) has seven electrons in the 
valence shell, and hence it lies in other group. 
7. (c) : As we move across a period, ionisation 
enthalpy increases, because of increased nuclear charge 
and decrease in atomic radii. However, abnormal values 
are observed for Be, N and Ne due to extra stability of 
half filled and fully filled orbitals. Thus, the actual order 
is, Li < B < Be < C < O < N < F < Ne. 
8. (d) : Na 2O - Basic oxide, Al 2O 3 - Amphoteric oxide, 
N 2O - Neutral oxide, Cl 2O 7 - Acidic oxide. 
9. (b) : In metals, on moving down the group, metallic 
character increases, so basic nature increases hence most 
acidic will be BeO. 
10. (a, d) : The correct order of increasing negative 
electron gain enthalpy is : I < Br < F < Cl due to 
electron-electron repulsion in small sized F atom and 
the correct order of increasing first ionisation enthalpy is 
B < C < O < N due to extra stability of half-filled orbitals 
in N-atom. 
11. (d) 
12. (None) : Cations lose electrons and are smaller in 
size than the parent atom, whereas anions add electrons 
and are larger in size than the parent atom. Hence, the order 
i s H
– 
> H > H
+
. 
For isoelectronic species, the ionic radii decreases with 
increase in atomic number i.e., nuclear charge. Hence, 
the correct orders are 
O
2– 
> F
– 
> Na
+ 
and N
3– 
> Mg
2+ 
> Al
3+
. 
Hints & Explanations 
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1. (d) : Unnilunium – Mendelevium ? (a)-(i) 
Unniltrium – Lawrencium ? (b)-(ii) 
Unnilhexium – Seaborgium ? (c)-(iii) 
Unununnium – Roentgenium ? (d) (iv) 
2. (a) : The electronic configuration of the element 
with Z = 114 (Flerovium) is [Rn]5f
14 
6d
10
7s
2
7p
2
. 
Hence, it belongs to carbon family which has the same 
outer electronic configuration. 
3. (a) : The   electronic   configuration   of    an    atom: 
1s
2 
2s
2 
2p
6 
3s
2 
3p
6 
3d
3 
4s
2
 
In the configuration, the last electron of the atom is 
filled in d-subshell as 3d
3
. Thus, this element belongs to 
d-block of the periodic table with group no. VB or 5. 
4. (c) : Atomic number of the given element is 15 and 
it belongs to group 15. Therefore atomic number of the 
element below the above element = 15 + 18 = 33. 
5. (c) : Electronic configuration of an element with 
Z = 33 is 1s
2
2s
2
2p
6
3s
2
3p
6
3d
10
4s
2
4p
3
. 
Hence, it lies in VA or 15
th 
group. 
6. (c) : Elements (a), (b) and (d) belong to the same 
group since each one of them has two electrons in valence 
shell. In contrast, element (c) has seven electrons in the 
valence shell, and hence it lies in other group. 
7. (c) : As we move across a period, ionisation 
enthalpy increases, because of increased nuclear charge 
and decrease in atomic radii. However, abnormal values 
are observed for Be, N and Ne due to extra stability of 
half filled and fully filled orbitals. Thus, the actual order 
is, Li < B < Be < C < O < N < F < Ne. 
8. (d) : Na 2O - Basic oxide, Al 2O 3 - Amphoteric oxide, 
N 2O - Neutral oxide, Cl 2O 7 - Acidic oxide. 
9. (b) : In metals, on moving down the group, metallic 
character increases, so basic nature increases hence most 
acidic will be BeO. 
10. (a, d) : The correct order of increasing negative 
electron gain enthalpy is : I < Br < F < Cl due to 
electron-electron repulsion in small sized F atom and 
the correct order of increasing first ionisation enthalpy is 
B < C < O < N due to extra stability of half-filled orbitals 
in N-atom. 
11. (d) 
12. (None) : Cations lose electrons and are smaller in 
size than the parent atom, whereas anions add electrons 
and are larger in size than the parent atom. Hence, the order 
i s H
– 
> H > H
+
. 
For isoelectronic species, the ionic radii decreases with 
increase in atomic number i.e., nuclear charge. Hence, 
the correct orders are 
O
2– 
> F
– 
> Na
+ 
and N
3– 
> Mg
2+ 
> Al
3+
. 
Hints & Explanations 
2 
20 
13. (d) Electron gain enthalpy becomes less negative 
from top to bottom in a group while it becomes more 
negative from left to right within a period. 
14. (b) : Acidic strength of hydrides increase with 
increase in molecular mass. 
Thus, order of acidic strength is 
HF < HCl < HBr < HI 
H 2O < H 2S < H 2 Se < H2Te 
NH 3 < PH 3 < AsH 3 < SbH 3 
and as acidic strength increases, pKa decreases. Thus 
order of pKa 
H 2O > H 2S > H 2Se > H 2 T e 
15. (a) : As positive charge on the cation increases, 
effective nuclear charge increases. Thus, atomic size 
decreases. 
16. (a) : Na ? Na
+ 
+ e
–
; ?H = 5.1 eV 
Na
+ 
+ e
– 
? Na ; ?H = –5.1 eV 
17. (a) : SnO 2 reacts with acid as well as base. So, SnO2
is an amphoteric oxide. 
SnO 2 + 4HCl ?? SnCl 2 + 2H 2O 
smallest size. Among the given species, Cs
+ 
has maximum 
size among given cations and F
–
 has smallest size among 
given anions, thus CsF has highest r c/ra ratio. 
22. (d) : Among options (a), (c) and (d), option (d) has 
the highest ionisation energy because of extra stability 
associated with half-filled 3 p-orbital. In option (b), the 
presence of 3 d
10 
electrons offers shielding effect, as a result 
the 4 p
3 
electrons do not experience much nuclear charge 
and hence, the electrons can be removed easily. 
23. (a) : Among isoelectronic ions, ionic radii of anions 
is more than that of cations. Further size of the anion 
increases with increase in negative charge and size of the 
cation decreases with increase in positive charge. 
24. (b) : The larger the atomic size, smaller is the value 
of the ionisation enthalpy. Again higher the screening 
effect, lesser is the value of ionisation potential. Hence, 
option (b) has lowest ionisation enthalpy. 
25. (a) : In going from left to right across a period in the 
periodic table, the basicity (i.e., proton affinity) decreases 
as the electronegativity of the atom possessing the lone 
pair of electrons increases. Hence, basicity of NH
–
 is 
SnO 2 + 2NaOH ?? Na 2 SnO 3 + H 2O – 
2
CaO is basic in nature while SiO 2 and CO 2 are acidic in 
n a t u r e . 
18. (c) : S
2– 
> Cl
– 
> K
+ 
> Ca
2+
 
Among isoelectronic species, ionic radii  increases  
with increase in negative charge. This happens because 
effective nuclear charge (Zeff) decreases. 
Similarly, ionic radii decreases with increase in positive 
charge as Zeff increases. 
19. (b) : Cl atom has the highest electron affinity in the 
periodic table. F being a member of group 17 has higher 
electron gain enthalpy than S which belongs to group 16. 
This in turn is higher than the electron affinity of O atom. 
Thus, Cl > F > S > O 
It is worth noting that the electron gain enthalpy of 
oxygen and fluorine, the members of the second period, 
have less negative values of electron gain enthalpy than 
the corresponding elements sulphur and chlorine of the 
third period. 
This is due to small size of the atoms of oxygen and 
fluorine. As a result, there is a strong inter-electronic 
repulsion when extra electron is added to these atoms, 
i.e., electron density is high and the addition of an extra 
electron is not easy. 
20. (b) : The atomic radii decrease on moving from left 
to right in a period, thus order of sizes for Cl, P and Mg 
is Cl < P < Mg. Down the group size increases. Thus, 
overall order is Cl < P < Mg < Ca. 
21. (b) : The cation to anion size ratio will be maximum 
when the cation is of largest size and the anion is of 
higher than F . On moving down a group, as the atomic 
size increases, basicity decreases. Hence, F
–
 is more basic 
than I
– 
and HO
– 
is more basic than HS
–
. Hence, among 
the given ionic species, NH 
–
 has maximum proton 
affinity. 
26. (d) : SeO 2 ?? acidic oxide, 
Al 2O 3, Sb 2O 3 ?? amphoteric, 
Bi 2O 3 ?? basic oxide. 
27. (a) : Na 2 O Basic character 
Na 2 S decreases down the group 
Na 2 Se 
Na2Te 
p H ? basic character 
Hence, pH 1 > pH 2 > pH 3 > pH4 
28. (a) 
29. (b) : Amongst isoelectronic ions, ionic radii of 
anions is more than that of cations. Further size of the 
anion increases with increase in –ve charge and size of 
cation decreases with increase in +ve charge. Hence, 
correct order is O
2– 
> F
– 
> Na
+ 
> Mg
2+ 
> Al
3+
. 
30. (b) : Li, Be, B, C - these elements belong to the same 
period. Generally the value of 1
st 
ionisation potential 
increases on moving from left to right in a period, since 
the nuclear charge of the elements also increase in the 
same direction. But the ionisation potential of boron   
(B ? 2s
2 
2p
1
) is lower than that of beryllium (Be ? 2s
2
), 
since in case of boron, 2p
1  
electron has to be removed 
to get B
+ 
while in case of Be (2s
2
), s-electron has to be 
removed to get Be
+  
(2s
1
). p-electron can be removed 
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1. (d) : Unnilunium – Mendelevium ? (a)-(i) 
Unniltrium – Lawrencium ? (b)-(ii) 
Unnilhexium – Seaborgium ? (c)-(iii) 
Unununnium – Roentgenium ? (d) (iv) 
2. (a) : The electronic configuration of the element 
with Z = 114 (Flerovium) is [Rn]5f
14 
6d
10
7s
2
7p
2
. 
Hence, it belongs to carbon family which has the same 
outer electronic configuration. 
3. (a) : The   electronic   configuration   of    an    atom: 
1s
2 
2s
2 
2p
6 
3s
2 
3p
6 
3d
3 
4s
2
 
In the configuration, the last electron of the atom is 
filled in d-subshell as 3d
3
. Thus, this element belongs to 
d-block of the periodic table with group no. VB or 5. 
4. (c) : Atomic number of the given element is 15 and 
it belongs to group 15. Therefore atomic number of the 
element below the above element = 15 + 18 = 33. 
5. (c) : Electronic configuration of an element with 
Z = 33 is 1s
2
2s
2
2p
6
3s
2
3p
6
3d
10
4s
2
4p
3
. 
Hence, it lies in VA or 15
th 
group. 
6. (c) : Elements (a), (b) and (d) belong to the same 
group since each one of them has two electrons in valence 
shell. In contrast, element (c) has seven electrons in the 
valence shell, and hence it lies in other group. 
7. (c) : As we move across a period, ionisation 
enthalpy increases, because of increased nuclear charge 
and decrease in atomic radii. However, abnormal values 
are observed for Be, N and Ne due to extra stability of 
half filled and fully filled orbitals. Thus, the actual order 
is, Li < B < Be < C < O < N < F < Ne. 
8. (d) : Na 2O - Basic oxide, Al 2O 3 - Amphoteric oxide, 
N 2O - Neutral oxide, Cl 2O 7 - Acidic oxide. 
9. (b) : In metals, on moving down the group, metallic 
character increases, so basic nature increases hence most 
acidic will be BeO. 
10. (a, d) : The correct order of increasing negative 
electron gain enthalpy is : I < Br < F < Cl due to 
electron-electron repulsion in small sized F atom and 
the correct order of increasing first ionisation enthalpy is 
B < C < O < N due to extra stability of half-filled orbitals 
in N-atom. 
11. (d) 
12. (None) : Cations lose electrons and are smaller in 
size than the parent atom, whereas anions add electrons 
and are larger in size than the parent atom. Hence, the order 
i s H
– 
> H > H
+
. 
For isoelectronic species, the ionic radii decreases with 
increase in atomic number i.e., nuclear charge. Hence, 
the correct orders are 
O
2– 
> F
– 
> Na
+ 
and N
3– 
> Mg
2+ 
> Al
3+
. 
Hints & Explanations 
2 
20 
13. (d) Electron gain enthalpy becomes less negative 
from top to bottom in a group while it becomes more 
negative from left to right within a period. 
14. (b) : Acidic strength of hydrides increase with 
increase in molecular mass. 
Thus, order of acidic strength is 
HF < HCl < HBr < HI 
H 2O < H 2S < H 2 Se < H2Te 
NH 3 < PH 3 < AsH 3 < SbH 3 
and as acidic strength increases, pKa decreases. Thus 
order of pKa 
H 2O > H 2S > H 2Se > H 2 T e 
15. (a) : As positive charge on the cation increases, 
effective nuclear charge increases. Thus, atomic size 
decreases. 
16. (a) : Na ? Na
+ 
+ e
–
; ?H = 5.1 eV 
Na
+ 
+ e
– 
? Na ; ?H = –5.1 eV 
17. (a) : SnO 2 reacts with acid as well as base. So, SnO2
is an amphoteric oxide. 
SnO 2 + 4HCl ?? SnCl 2 + 2H 2O 
smallest size. Among the given species, Cs
+ 
has maximum 
size among given cations and F
–
 has smallest size among 
given anions, thus CsF has highest r c/ra ratio. 
22. (d) : Among options (a), (c) and (d), option (d) has 
the highest ionisation energy because of extra stability 
associated with half-filled 3 p-orbital. In option (b), the 
presence of 3 d
10 
electrons offers shielding effect, as a result 
the 4 p
3 
electrons do not experience much nuclear charge 
and hence, the electrons can be removed easily. 
23. (a) : Among isoelectronic ions, ionic radii of anions 
is more than that of cations. Further size of the anion 
increases with increase in negative charge and size of the 
cation decreases with increase in positive charge. 
24. (b) : The larger the atomic size, smaller is the value 
of the ionisation enthalpy. Again higher the screening 
effect, lesser is the value of ionisation potential. Hence, 
option (b) has lowest ionisation enthalpy. 
25. (a) : In going from left to right across a period in the 
periodic table, the basicity (i.e., proton affinity) decreases 
as the electronegativity of the atom possessing the lone 
pair of electrons increases. Hence, basicity of NH
–
 is 
SnO 2 + 2NaOH ?? Na 2 SnO 3 + H 2O – 
2
CaO is basic in nature while SiO 2 and CO 2 are acidic in 
n a t u r e . 
18. (c) : S
2– 
> Cl
– 
> K
+ 
> Ca
2+
 
Among isoelectronic species, ionic radii  increases  
with increase in negative charge. This happens because 
effective nuclear charge (Zeff) decreases. 
Similarly, ionic radii decreases with increase in positive 
charge as Zeff increases. 
19. (b) : Cl atom has the highest electron affinity in the 
periodic table. F being a member of group 17 has higher 
electron gain enthalpy than S which belongs to group 16. 
This in turn is higher than the electron affinity of O atom. 
Thus, Cl > F > S > O 
It is worth noting that the electron gain enthalpy of 
oxygen and fluorine, the members of the second period, 
have less negative values of electron gain enthalpy than 
the corresponding elements sulphur and chlorine of the 
third period. 
This is due to small size of the atoms of oxygen and 
fluorine. As a result, there is a strong inter-electronic 
repulsion when extra electron is added to these atoms, 
i.e., electron density is high and the addition of an extra 
electron is not easy. 
20. (b) : The atomic radii decrease on moving from left 
to right in a period, thus order of sizes for Cl, P and Mg 
is Cl < P < Mg. Down the group size increases. Thus, 
overall order is Cl < P < Mg < Ca. 
21. (b) : The cation to anion size ratio will be maximum 
when the cation is of largest size and the anion is of 
higher than F . On moving down a group, as the atomic 
size increases, basicity decreases. Hence, F
–
 is more basic 
than I
– 
and HO
– 
is more basic than HS
–
. Hence, among 
the given ionic species, NH 
–
 has maximum proton 
affinity. 
26. (d) : SeO 2 ?? acidic oxide, 
Al 2O 3, Sb 2O 3 ?? amphoteric, 
Bi 2O 3 ?? basic oxide. 
27. (a) : Na 2 O Basic character 
Na 2 S decreases down the group 
Na 2 Se 
Na2Te 
p H ? basic character 
Hence, pH 1 > pH 2 > pH 3 > pH4 
28. (a) 
29. (b) : Amongst isoelectronic ions, ionic radii of 
anions is more than that of cations. Further size of the 
anion increases with increase in –ve charge and size of 
cation decreases with increase in +ve charge. Hence, 
correct order is O
2– 
> F
– 
> Na
+ 
> Mg
2+ 
> Al
3+
. 
30. (b) : Li, Be, B, C - these elements belong to the same 
period. Generally the value of 1
st 
ionisation potential 
increases on moving from left to right in a period, since 
the nuclear charge of the elements also increase in the 
same direction. But the ionisation potential of boron   
(B ? 2s
2 
2p
1
) is lower than that of beryllium (Be ? 2s
2
), 
since in case of boron, 2p
1  
electron has to be removed 
to get B
+ 
while in case of Be (2s
2
), s-electron has to be 
removed to get Be
+  
(2s
1
). p-electron can be removed 
Classification of Elements and Periodicity in Properties 
more easily than s-electron so the energy required to 
remove electron will be less in case of boron. The order 
will be 
Li < B < Be < C. 
31. (a) : The energy required to remove the most 
loosely bound electron from an isolated gaseous atom is 
called the ionisation energy. 
The ionisation potential increases as the size of the atom 
decreases. Atoms with fully or partly filled orbitals have 
high ionisation potential. 
32. (c) : Among the halogens the electron affinity value 
of ‘F’ should be maximum. But due to small size there is 
inter-electronic repulsion thus, there is difficulty in entry 
of new electrons. Thus, the E.A. value is slightly lower 
than chlorine and the order is I < Br < F < Cl. 
33. (d) : 4Be ? 1s
2 
2s
2
, 5B ? 1s
2 
2s
2 
2p
1
 
Due to stable fully-filled ‘s’-orbital arrangement of 
electrons in ‘Be’ atom, more energy is required to 
remove an electron from the valence shell than ‘B’-atom. 
Therefore ‘Be’ has higher ionisation potential than ‘B’. 
34. (b) : Positive ion is always smaller and negative ion 
is always larger than the parent atom. 
35. (d) : Since all of these ions contain 18 electrons  
each, so these are isoelectronic. For isoelectronic ions, 
the anion having large negative charge is the largest in 
size i.e., S
2–
. 
36. (a) : These are isoelectronic ions (ions with same 
number of electrons) and for isoelectronic ions, greater 
the positive charge, greater is the force of attraction on 
the electrons by the nucleus and the smaller is the size of 
the ion. Thus, Al
3+ 
has the smallest size. 
21 
37. (b) : Al 2O 3 and ZnO are amphoteric. N 2O 5 is 
strongly acidic. MgO is the most basic. 
38. (c) : The cations are always smaller than the neutral 
atom and anions are always larger in size, Na
– 
> Na > Na
+
. 
39. (c) : In isoelectronic ions, the size of the cation 
decreases as the magnitude of the positive charge 
increases. 
40. (d) : Within a period from left to right, atomic 
volume first decreases and then increases. 
41. (d) : Abnormally high difference between 2
nd 
and 
3
rd 
ionisation energy means that the element has two 
valence electrons, which is a case in configuration (d). 
42. (d) 
43. (c) : The order of ionic size for given ions will be 
K
+ 
> Ca
2+ 
> Mg
2+ 
and that of Cl
– 
> F
–
. Therefore, MgCl 2
has minimum value of cation/anion (Mg
2+
/Cl
–
) ratio. 
44. (c) : N, O and F are highly electronegative non- 
metals and will have the strongest tendency to form 
anions by gaining electrons from metal atoms. 
45. (c) : As halogens have seven electrons (ns
2
np
5
) in 
the valence shell, they have a strong tendency to acquire 
the nearest inert gas configuration by gaining an electron 
from the metallic atom and form halide ions easily. 
46. (a) : Metallic character decreases in a period and 
increases in a group. 
47. (c) : The atomic size decreases within a period from 
left to right, therefore Li > Be and Na > Mg. The size 
increases in a group from top to bottom. Hence, the size 
of Na is greater than Li. Overall order Na > Mg > Li > Be. 
Thus, Be has smallest size. 
??? ?