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All questions of d- and f-Block Elements for NEET Exam

Transition metals with highest melting point is
  • a)
    Cr
  • b)
    W
  • c)
    Hg
  • d)
    Sc
Correct answer is option 'B'. Can you explain this answer?

W belongs to 5d series and also it have lot of unpaired electrons thus it forms strong metallic bonding.

Lucas reagent is
  • a)
    ZnCl2 + HCl
  • b)
    MnO2 + H2O
  • c)
    H2SO+ HCl
  • d)
    NO + H2O
Correct answer is option 'A'. Can you explain this answer?

Lucas Test is done to distinguish primary secondary and tertiary alcohols. Lucas reagent is ZnCl2 + HCl

For the four successive transition elements (Cr, Mn, Fe and Co), the stability of +2 oxidation state will be there in which of the following order?
  • a)
    Mn > Fe > Cr > Co [2011]
  • b)
    Fe > Mn > Co > Cr
  • c)
    Co > Mn > Fe > Cr
  • d)
    Cr > Mn > Co > Fe
Correct answer is option 'A'. Can you explain this answer?

Kalyan Chavan answered
B)Fe
c)Co
d)Cr

The correct answer is: d) Cr

The stability of the +2 oxidation state decreases as we move from Cr to Co. This is because the effective nuclear charge experienced by the valence electrons increases as we move from left to right in a period, making it more difficult for the element to lose electrons and form a positive ion. Additionally, the electron configuration of Cr2+ (3d4) is more stable than that of Mn2+ (3d5), Fe2+ (3d6), and Co2+ (3d7) due to half-filled and fully-filled subshells being more stable. Therefore, the stability of the +2 oxidation state follows the order Cr > Mn > Fe > Co.

The catalytic activity of transition metals and their compounds is ascribed mainly to :[2012 M]
  • a)
    their magnetic behaviour
  • b)
    their unfilled d-orbitals
  • c)
    their ability to adopt variable oxidation state
  • d)
    their chemical reactivity
Correct answer is option 'C'. Can you explain this answer?

The transition metals and their compounds are used as catalysts. Because of the variable oxidation states, due to this, they easily absorb and re-emit wide range of energy to provide the necessary activation energy.

Which of the following ion has smallest radii?
  • a)
    V2+
  • b)
    Ni2+
  • c)
    Mn2+
  • d)
    Ti2+
Correct answer is option 'B'. Can you explain this answer?

Preethi Bose answered
In period when we move from left to right in a period atomic radii 1st decreases till nickel then starts increasing so Ni2+ has smallest radii.

The correctorder of decreasing second ionisation enthalpy of Ti (22), V(23), Cr(24) and Mn (25) is : [2008]
  • a)
    Cr > Mn > V > Ti
  • b)
    V > Mn > Cr > Ti
  • c)
    Mn > Cr > Ti > V
  • d)
    Ti > V > Cr > Mn
Correct answer is option 'A'. Can you explain this answer?

Nilotpal Gupta answered
Ti ; Z (22) is 1s22s22p63s23p64s23d2
V ; Z (23) is 1s22s22p63s23p64s23d3
Cr ; Z (24) is 1s22s22p63s23p63d54s1
Mn ; Z (25) is 1s22s22p63s23d54s2
 The second electron in all the cases (except Cr) is taken out from 4s-orbital and for Cr it is an electron from completely half filled 3d-orbital. The force required for removal of second electron will be more for Mn (except for Cr) having more positive charge.
Based on this we find the correct order is Mn > V > Ti.  Cr > Mn > V > Ti. So correct answeris (a).

In which of the following pairs are both the ions coloured in aqueous solutions ? [2006]         (At. no. : Sc = 21, Ti = 22, Ni = 28, Cu = 29, Co = 27)
  • a)
    Sc3+, Ti3+
  • b)
    Sc3+, Co2+
  • c)
    Ni2+, Cu+
  • d)
    Ni2+, Ti3+
Correct answer is option 'D'. Can you explain this answer?

Dipanjan Mehta answered
Sc3+ : 1s2, 2s2p6, 3s2p6d0, 4s0; no unpaired electron.
Cu+ : 1s2, 2s2p6, 3s2p6d10, 4s0; no unpaired electron.
Ni2+: 1s2, 2s2p6, 3s2p6d8, 4s0; unpaired electron present.
Ti3+ : 1s2, 2s2p6, 2s2p6d1, 4s0; unpaired electron present Co2+ : 1s2, 2s2p6, 3s2p6d7, 4s0; unpaired electron present So from the given option the only correct combination is Ni2+ and Ti3+

Ferrous sulphate on heating gives
  • a)
    SO2 and SO3
  • b)
    SO2 and O2
  • c)
    SO2
  • d)
    SO3
Correct answer is option 'A'. Can you explain this answer?

M. Vishnu answered
On heating, ferrous sulphate crystals lose water and anhydrous ferrous sulphate (FeSO4) is formed. So their colour changes from light green to white. On furtherheating, anhydrous ferrous sulphate decomposes to form ferric oxide (Fe2O3), sulphur dioxide (SO2) and sulphur trioxide (SO3).

Lanthanoids are [2004]
  • a)
    14 elements in the sixth period (atomic no. = 90 to 103) that are filling 4f sublevel
  • b)
    14 elements in the seventh period (atomic no. = 90 to 103) that are filling 5f sublevel
  • c)
    14 elements in the sixth period (atomic no. = 58 to 71) that are filling 4f sublevel
  • d)
    14 elements in the seventh period (atomic no. = 58 to 71) that are filling 4f sublevel
Correct answer is option 'C'. Can you explain this answer?

Athira Datta answered
The correct answer is option C: 14 elements in the sixth period (atomic no. = 58 to 71) that are filling the 4f sublevel.

Explanation:
- The periodic table is organized into periods and groups. The periods are horizontal rows, and the groups are vertical columns.
- The lanthanoids, also known as the lanthanides, are a group of elements that belong to the f-block of the periodic table.
- The lanthanoid series consists of 14 elements that fill the 4f sublevel. These elements have atomic numbers ranging from 58 to 71.
- The 4f sublevel is part of the fourth energy level (n=4) and is characterized by its unique electron configuration.
- In the lanthanoid series, the 4f sublevel is gradually filled up as you move across the period. Each element in the series adds one more electron to the 4f sublevel until it is completely filled.
- The lanthanoids are located in the sixth period of the periodic table because they correspond to the filling of the 4f sublevel.
- The lanthanoids are known for their similar chemical properties, which arise from the filling of the 4f sublevel. They are generally soft, malleable metals with high melting points and good electrical conductivity.
- Some common examples of lanthanoids include cerium (Ce), praseodymium (Pr), and europium (Eu).
- It's important to note that the atomic numbers of the lanthanoids range from 58 to 71, not from 90 to 103 as mentioned in options A and B. The atomic numbers from 90 to 103 correspond to a different series of elements called the actinoids, which fill the 5f sublevel.
- Therefore, the correct answer is option C: 14 elements in the sixth period (atomic no. = 58 to 71) that are filling the 4f sublevel.

Maximum magnetic moment is shown by
  • a)
    d6
  • b)
    d8
  • c)
    d5
  • d)
    d7
Correct answer is option 'C'. Can you explain this answer?

Magnetic Moment and d-orbitals


To understand why the maximum magnetic moment is shown by d5, we need to understand the concept of magnetic moment and the behavior of d-orbitals in transition metals.


Magnetic Moment


Magnetic moment is a measure of the strength and orientation of a magnet in a magnetic field. In the context of transition metals, it refers to the magnetic properties of unpaired electrons in the d-orbitals. The magnetic moment can be calculated using the formula:


Magnetic moment (μ) = √[n(n+2)] BM


Where n is the number of unpaired electrons and BM is the Bohr magneton, a unit of magnetic moment.


d-orbitals


d-orbitals are the five orbitals (dxy, dxz, dyz, dx²-y², dz²) available for electrons to occupy in the d-subshell. These orbitals have different shapes and orientations, and they can accommodate a maximum of 10 electrons.


Explanation


In the given options, the maximum magnetic moment is shown by d5. Let's analyze each option to understand why d5 has the highest magnetic moment.



  • d6: In d6 configuration, there are 4 unpaired electrons. Applying the magnetic moment formula, we get μ = √[4(4+2)] BM = √24 BM.

  • d8: In d8 configuration, there are 2 unpaired electrons. Applying the magnetic moment formula, we get μ = √[2(2+2)] BM = √8 BM.

  • d5: In d5 configuration, there are 5 unpaired electrons. Applying the magnetic moment formula, we get μ = √[5(5+2)] BM = √35 BM.

  • d7: In d7 configuration, there are 3 unpaired electrons. Applying the magnetic moment formula, we get μ = √[3(3+2)] BM = √15 BM.



Comparing the magnetic moments calculated for each option, we can see that d5 has the highest magnetic moment of √35 BM. Therefore, the correct answer is option 'C'.


It is important to note that the magnetic moment depends on the number of unpaired electrons. The more unpaired electrons present in the d-orbitals, the higher the magnetic moment. This is because unpaired electrons have individual magnetic moments that align with an external magnetic field, resulting in a stronger overall magnetic moment.

Which of the following pairs of ions have same paramagnetic moment?
  • a)
    Cu2+, Ti3+
  • b)
    Ti3+, Ni2+
  • c)
    Ti4+, Cu2+
  • d)
    Mn2+, Cu2+
Correct answer is option 'A'. Can you explain this answer?

Ameya Pillai answered
Explanation:

Paramagnetic Moment:
Paramagnetic substances are those substances that are weakly attracted by an external magnetic field. The paramagnetic moment is a measure of the strength of this attraction. It is given by the formula:

Paramagnetic Moment (μ) = √(n(n+2)) BM

Where:
- n is the number of unpaired electrons in the atom or ion
- BM stands for Bohr Magneton, a unit of magnetic moment.

Identifying the Number of Unpaired Electrons:
To determine which pairs of ions have the same paramagnetic moment, we need to first identify the number of unpaired electrons in each ion. Unpaired electrons are those that do not have a partner or are not paired with another electron in the same orbital.

Calculating the Number of Unpaired Electrons:
To calculate the number of unpaired electrons, we need to know the electron configuration of each ion. Let's calculate the number of unpaired electrons for each pair of ions:

a) Cu2+ (Copper ion with +2 charge)
- The electron configuration of Cu2+ is: 1s2 2s2 2p6 3s2 3p6 3d9
- In Cu2+, there are 9 electrons in the 3d orbital, which means there is 1 unpaired electron.

b) Ti3+ (Titanium ion with +3 charge)
- The electron configuration of Ti3+ is: 1s2 2s2 2p6 3s2 3p6 3d1
- In Ti3+, there is 1 electron in the 3d orbital, which means there is 1 unpaired electron.

c) Ti4+ (Titanium ion with +4 charge)
- The electron configuration of Ti4+ is: 1s2 2s2 2p6 3s2 3p6
- In Ti4+, all the electrons are paired, which means there are no unpaired electrons.

d) Mn2+ (Manganese ion with +2 charge)
- The electron configuration of Mn2+ is: 1s2 2s2 2p6 3s2 3p6 3d5
- In Mn2+, there are 5 electrons in the 3d orbital, which means there are 5 unpaired electrons.

Comparing the Number of Unpaired Electrons:
From the calculations above, we can see that:
- Cu2+ and Ti3+ both have 1 unpaired electron.
- Ti4+ and Mn2+ have 0 unpaired electrons.

Conclusion:
Based on the number of unpaired electrons, we can conclude that the pair of ions with the same paramagnetic moment is:
a) Cu2+ (1 unpaired electron)
b) Ti3+ (1 unpaired electron)

Which among the following transition metal has lowest melting point?
  • a)
    Titanium
  • b)
    Cobalt
  • c)
    Mercury
  • d)
    Scandium
Correct answer is option 'C'. Can you explain this answer?

Srestha Patel answered
Understanding Melting Points of d-Block Elements
The melting points of d-block elements vary significantly due to their unique electron configurations and bonding characteristics. Among the options provided, we will analyze why mercury has the lowest melting point.
Factors Influencing Melting Points
- Electron Configuration: Transition metals have varying numbers of d-electrons, influencing their bonding and stability.
- Metallic Bonding: Stronger metallic bonds generally lead to higher melting points. The presence of d-electrons contributes to the strength of these bonds.
- Atomic Structure: The arrangement of atoms and the presence of any additional forces (like van der Waals forces) can also affect melting points.
Analysis of Each Element
- Titanium (Ti):
- Has a melting point of approximately 1668°C.
- Strong metallic bonds due to a larger number of d-electrons.
- Cobalt (Co):
- Melting point around 1495°C.
- Exhibits significant metallic bonding strength.
- Scandium (Sc):
- Melting point is about 1541°C.
- More stable due to its electron configuration but still has a higher melting point than mercury.
- Mercury (Hg):
- Notably has a melting point of -38.83°C.
- Exists as a liquid at room temperature, indicating weak metallic bonding and minimal d-electron participation in bonding.
Conclusion
Mercury's unique properties, including its liquid state at room temperature and weak metallic bonds, result in its significantly lower melting point compared to titanium, cobalt, and scandium. Thus, the correct answer is option 'C', mercury, which has the lowest melting point among the listed d-block elements.

The main reason for larger number of oxidation states exhibited by the actinoids than the corresponding lanthanoids, is [2005, 2006]
  • a)
    more energy difference between 5f and 6d orbitals than between 4f and 5d orbitals.
  • b)
    lesser energy difference between 5f and 6d orbitals than between 4f and 5d orbitals.
  • c)
    larger atomic size of actinoids than the lanthanoids.
  • d)
    greater reactive nature of the actinoids than the lanthanoids.
Correct answer is option 'B'. Can you explain this answer?

Nilotpal Gupta answered
The cause of showing different oxidation is due to the fact that there is only a small difference between the energies of electron in the ns orbitals and (n – 1)d orbitals with the result both ns as well (n – 1)d electrons can be used for compound formation. Lesser energy difference between 5f and 6d orbitals than between 4f and 5d orbitals result in larger no. of oxidation state.

Which of the following oxidation states are the most characteristic for lead and tin respectively?
  • a)
    + 2, + 4
  • b)
    + 4, + 4 [2007]
  • c)
    + 2, + 2
  • d)
    + 4, + 2
Correct answer is option 'A'. Can you explain this answer?

The oxidation states of lead and tin can vary depending on the compound they are present in. However, there are certain oxidation states that are more characteristic for these elements.

Lead:
- The most characteristic oxidation state for lead is +2. This means that lead can lose two electrons to form a 2+ cation. This oxidation state is commonly observed in lead compounds such as lead(II) oxide (PbO), lead(II) chloride (PbCl2), and lead(II) nitrate (Pb(NO3)2).

Tin:
- The most characteristic oxidation state for tin is +4. This means that tin can lose four electrons to form a 4+ cation. This oxidation state is commonly observed in tin compounds such as tin(IV) oxide (SnO2), tin(IV) chloride (SnCl4), and tin(IV) sulfate (Sn(SO4)2).

Explanation:
- The oxidation state of an element refers to the charge that element would have if all its bonds were ionic. It is a measure of the electron gain or loss of an atom in a compound.
- In the case of lead, it has a tendency to lose two electrons to achieve a stable configuration. This results in its most characteristic oxidation state of +2.
- Similarly, tin has a tendency to lose four electrons to achieve a stable configuration. This results in its most characteristic oxidation state of +4.
- It is important to note that lead and tin can also exhibit other oxidation states depending on the compound they are present in. For example, lead can also exist in the +4 oxidation state in compounds such as lead(IV) oxide (PbO2), while tin can also exist in the +2 oxidation state in compounds such as tin(II) chloride (SnCl2).
- However, the most characteristic oxidation states for lead and tin respectively are +2 and +4.
- Therefore, the correct answer is option A, which states that the most characteristic oxidation states for lead and tin are 2 and 4 respectively.

Identify the incorrect statement among the following: [2007]
  • a)
    Lanthanoid contraction is the accumulation of successive shrinkages.
  • b)
    As a result of lanthanoid contraction, the properties of 4d series of the transition elements have no similarities with the 5d series of elements.
  • c)
    Shielding power of 4f electron s is qui te weak.
  • d)
    There is a decrease in the radii of the atoms or ions as one proceeds from La to Lu.
Correct answer is option 'B'. Can you explain this answer?

Rohan Unni answered
There is a steady decrease in the radii as the atomic number of the lanthanide elements increases. For every additional proton added in nucleus the corresponding electron goes to 4f subshell.
The shape of f -orbitals is very much diffused and they have poor shielding effect. The effective nuclear charge increases which causes the contraction in the size of electron charge cloud. This contraction in size is quite regular and known as Lanthanoid contraction.
Since the change in the ionic radii in the lanthanide series is very small, thus their chemical properties are similar.

Qut of TiF62–, CoF63–, Cu2Cl2 and  NiCl24– (Z of Ti = 22, Co = 27, Cu = 29, Ni = 28), the colourless species are: [2009]
  • a)
    Cu2Cl2 and NiCl24–
  • b)
    TiF62–,and Cu2Cl2
  • c)
    CoF63– ,and NiCl24–
  • d)
    TiF62–,and CoF63–
Correct answer is option 'B'. Can you explain this answer?

The colour exhibited by transition metal ions is due to the presence of unpaired electrons in -orbitals which permits the  - excitation of electrons.
 Ti is in + 4 O.S. ; 3d0 = colourless
 Co is in + 3 O.S ; 3d5 = coloured
In Cu2Cl2– Cu is in +1 O.S. ; 3d10 – colourless
  Ni is in + 2 O.S ; 3d8 – coloured

Which of the following lanth anoidions is diamagnetic ? (At nos. Ce = 58, Sm = 62, Eu = 63, Yb = 70) [NEET 2013]
  • a)
    Sm2+
  • b)
    Eu2+
  • c)
    Yb2+
  • d)
    Ce2+
Correct answer is option 'C'. Can you explain this answer?

Rhea Iyer answered
Diamagnetic materials are those that have all their electrons paired up in their atomic or molecular orbitals, resulting in no net magnetic moment. On the other hand, paramagnetic materials have unpaired electrons and exhibit a net magnetic moment.

In the given options, we need to identify the lanthanoid anion that is diamagnetic.

Let's analyze each option one by one:

a) Sm2: Samarium (Sm) has an atomic number of 62. In its neutral state, it has the electron configuration [Xe] 4f6 6s2. Sm2 would mean that two electrons are removed from the 6s orbital. The resulting electron configuration would be [Xe] 4f6. Since there are unpaired electrons present, Sm2 is paramagnetic and not diamagnetic.

b) Eu2: Europium (Eu) has an atomic number of 63. In its neutral state, it has the electron configuration [Xe] 4f7 6s2. Eu2 would mean that two electrons are removed from the 6s orbital. The resulting electron configuration would be [Xe] 4f7. Since there are unpaired electrons present, Eu2 is paramagnetic and not diamagnetic.

c) Yb2: Ytterbium (Yb) has an atomic number of 70. In its neutral state, it has the electron configuration [Xe] 4f14 6s2. Yb2 would mean that two electrons are removed from the 6s orbital. The resulting electron configuration would be [Xe] 4f14. Since all the orbitals are completely filled and there are no unpaired electrons, Yb2 is diamagnetic.

d) Ce2: Cerium (Ce) has an atomic number of 58. In its neutral state, it has the electron configuration [Xe] 4f1 5d1 6s2. Ce2 would mean that two electrons are removed from the 6s orbital. The resulting electron configuration would be [Xe] 4f1 5d1. Since there is an unpaired electron present in the 4f orbital, Ce2 is paramagnetic and not diamagnetic.

Therefore, the correct answer is option C, Yb2, as it is the only lanthanoid anion that has a completely filled f-orbital and no unpaired electrons, making it diamagnetic.

The basic character of the transition metal monoxides follows the order [2003] (Atomic Nos.,Ti = 22, V = 23, Cr = 24, Fe = 26)
  • a)
    TiO > VO > CrO > FeO
  • b)
    VO > CrO > TiO > FeO
  • c)
    CrO > VO > FeO > TiO
  • d)
    TiO > FeO > VO > CrO
Correct answer is option 'A'. Can you explain this answer?

Gauri Khanna answered
The basic character of the transition metal monoxides follows the order:

TiO < v2o="">< cro=""><>

This means that TiO is the least basic, while FeO is the most basic among the given transition metal monoxides.

The outer electronic configuration of Gd (At. No. 64) is: [NEET Kar. 2013]
  • a)
     4f3 5d5 6s
  • b)
    4f8 5d0 6s2
  • c)
     4f7 5d1 6s2
  • d)
    4f4 5d6s2 
Correct answer is option 'C'. Can you explain this answer?

Tanisha Shah answered
Answer of this question can be easily obtain from d and f block chapter
it is an element of lanthanoid series
Due to stability of half filled orbital answer is c

Which is least soluble in water?
  • a)
    Ag2S
  • b)
    AgBr
  • c)
    AgCl
  • d)
    AgI
Correct answer is option 'A'. Can you explain this answer?

Alok Mehta answered
Water is polar. Using the axiom, “like dissolves like”, hexane would water- insoluble. CH3OH, CH3CO2H and CH3NH2 are polar and can participate in hydrogen- bonding interactions with water, which would make these compounds quite water- soluble.Silver sulfide (Ag 2S) is the sulfide of silver. It is useful as a photosensitizer in photography. .... The crystallography of silver sulfide, Ag2S. Zeitschrift fur ... Ag2S. least soluble in water

KMnO4 can be prepared from K2MnO4 as per the reaction:
The reaction can go to completion by removing OH ions by adding. [NEET 2013]
  • a)
    KOH
  • b)
    CO2
  • c)
    SO2
  • d)
    HCl
Correct answer is option 'B'. Can you explain this answer?

Ayush Chavan answered
HCl and SO2 are reducing agents and can reduce MnO4. CO2 which is neither oxidising and nor reducing will provide only acidic medium. It can shift reaction in forward direction and reaction can go to completion.

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