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All questions of d – and f – Block Elements for JEE Exam

Can you explain the answer of this question below:
Which one of the following is a diamagnetic ion?
  • A:
    CO2+
  • B:
    Cu2+
  • C:
    Mn2+
  • D:
    Sc3+
The answer is d.

Co+2 = [Ar] 3d7
Cu2+ = [Ar] 3d9
Mn+2 = [Ar] 3d5
Sc+3 = [Ar]
We can see that only Sc+3  has no unpaired electron, so it is a diamagnetic ion.

Which ion will show more paramagnetic behaviour ?
  • a)
    Cu+
  • b)
    Fe2+
  • c)
    Ag+
  • d)
    Fe3+
Correct answer is option 'D'. Can you explain this answer?

Lavanya Menon answered
Since the configuration of Fe3+ ion is (argon ) 3d5,which contains maximum number of unpaired electrons, hence more will be paramagnetic behavior.

Which form of silver is colourless?
  • a)
    Ag2+
  • b)
    Ag
  • c)
    Ag3+
  • d)
    Ag+
Correct answer is option 'D'. Can you explain this answer?

Om Desai answered
ilver in the form of Ag+ is colourless. For transition metal ions to exhibit color, their metal ions must have incompletely filled (n-1)d orbitals.
Ag+ =4d10,5s0
Ag+ has completely filled d orbitals hence is colourless.

 Which among the following is colourless?
  • a)
    Sc2+
  • b)
    Zn2+
  • c)
    Ti3+
  • d)
    V3+
Correct answer is option 'B'. Can you explain this answer?

Krishna Iyer answered
Zn2+ has completely filled d-orbitals and there are no vacant d-orbitals for the transition of electrons, hence it is colourless.

The first ionization energy of the d-block elements are?
  • a)
    Lesser than p-block elements
  • b)
    Between s and p-block elements
  • c)
    Lesser than s-block elements
  • d)
    Higher than p-block elements
Correct answer is option 'B'. Can you explain this answer?

Rahul Bansal answered
The first ionization energy of the d-block elements are between s and p-block elements. Thus they are more electropositive than p-block elements and less electropositive than s-block elements.

 In which of the following oxidation states La achieve the noble gas configuration?
  • a)
    +7
  • b)
    +3
  • c)
    +5
  • d)
    +2
Correct answer is option 'B'. Can you explain this answer?

Shail Chawla answered
La stands for Lanthanum, which is a member of the lanthanide series of elements in the periodic table. It has an atomic number of 57 and an electronic configuration of [Xe]5d1 6s2.

Achieving Noble Gas Configuration
To achieve a noble gas configuration, an element must have its outermost shell filled with electrons. The noble gases are stable because they have a filled outermost shell. Lanthanum can achieve this configuration by losing three electrons from its outermost shell.

Oxidation States
The oxidation state of an element is the charge that it carries when it forms a compound or ion. Lanthanum can form compounds in various oxidation states, including +2, +3, and +4.

In order to determine in which oxidation state La achieves noble gas configuration, we need to look at its electron configuration and determine how many electrons it needs to lose to achieve a filled outermost shell.

La3+ (Oxidation State of +3)
When Lanthanum loses three electrons, it forms a +3 ion (La3+). In this oxidation state, La has a noble gas configuration of [Xe]. Therefore, option B is the correct answer.

Other Oxidation States
Lanthanum can also form compounds in other oxidation states, but they do not achieve a noble gas configuration. For example, in the +2 oxidation state, La has an electron configuration of [Xe]5d1, which is not a filled outermost shell.

Conclusion
In conclusion, Lanthanum achieves noble gas configuration in the +3 oxidation state by losing three electrons and forming a La3+ ion.

Which of the following group of elements are not regarded as transition elements?
  • a)
    Sc,Y,La
  • b)
    Cu, Ag, Au
  • c)
    Zn, Cd, Hg
  • d)
    Cr ,Mo,W
Correct answer is option 'C'. Can you explain this answer?

Neha Sharma answered
Zn, Cd & Hg because the d-orbital of these elements are completely filled. So, they don't show the characteristics of transition elements (i.e. the d-orbital of transition elements is incomplete.

 The inner transition elements are the elements in which the added electrons go to:
  • a)
    (n-1)d-orbitals
  • b)
    (n-1)d-orbitals and (n-1)f-orbitals
  • c)
    (n-1)d-orbitals and ns orbitals
  • d)
    (n-2)f-orbitals
Correct answer is option 'D'. Can you explain this answer?

Rohit Shah answered
 Lanthanides and actinides are called inner transition elements because they are a group of elements that are shown as the bottom two rows of the periodic table. ... Lanthanides and actinides belong to the f-block elements, which means that they have filled up their f-orbitals with electrons.

 Which of the following group contain mostly radioactive elements ?
  • a)
    Lanthanoids
  • b)
    3 d transition series
  • c)
    4 d transition series
  • d)
    Actinoids
Correct answer is option 'D'. Can you explain this answer?

Parth Sharma answered
The actinoids are said to be most radioactive metals because in this group all the metals have very oxidation number and are very rare metals found on earth and it has all the elements radioactive in its group and it has most radioactive metal uranium in it's group.

 Mischmetal is an alloy of:
    • a)
      Lanthanoid metal and Iron
    • b)
      Actinoid metal and Iron
    • c)
      Manganese, nickel and iron
    • d)
      Zinc ,cobalt and iron
    Correct answer is option 'A'. Can you explain this answer?

    Snehal Iyer answered
    Explanation:

    Mischmetal is an alloy of Lanthanoid Metal and Iron. It is a rare earth alloy, which is primarily used in the production of alloy steels, stainless steels, and other high-performance alloys.

    Composition:

    Mischmetal typically contains 50-55% cerium, 20-25% lanthanum, and small amounts of other rare earth metals such as neodymium, praseodymium, and gadolinium. The remaining portion of the alloy is typically iron.

    Properties:

    Mischmetal has a number of unique properties that make it an attractive alloy for use in a variety of applications. These properties include:

    - High heat resistance
    - High strength and durability
    - Corrosion resistance
    - Good machinability

    Applications:

    Mischmetal is primarily used in the production of alloy steels, stainless steels, and other high-performance alloys. It is also used in the production of magnesium alloys, which are used in a variety of applications, including aerospace, automotive, and sporting goods.

    Some other applications of Mischmetal are:

    - In the production of lighter flints
    - As a pyrophoric material for the ignition of torches and lighters
    - In the production of certain types of electrodes for welding and cutting
    - In the production of certain types of batteries

    Conclusion:

    In conclusion, Mischmetal is an alloy of lanthanoid metal and iron, primarily used in the production of alloy steels, stainless steels, and other high-performance alloys. It has a number of unique properties that make it an attractive alloy for use in a variety of applications.

     Melting point of d block elements across a period:
    • a)
      Increases from left to right
    • b)
      Deceases from left to right
    • c)
      Increases to a maximum at d5 and then decreases with increase of atomic number.
    • d)
      Does not change on moving from left to right.
    Correct answer is option 'C'. Can you explain this answer?

    Jayant Mishra answered
    The melting and boiling points first increase, reaches maximum and then steadily decrease across any transition series. ... The low melting points of Zn, Cd, and Hg are due to the absence of unpaired d-electrons in their atoms and thus low metallic bonding.

    Number of electrons with l = 2 and s = 1/2 in zinc atom are
      Correct answer is '5'. Can you explain this answer?

      Krishna Iyer answered
      l = 2 means d-subshell. Zinc has 10 electrons ind-subshell in which 5 electrons are + 1/2 spin and 5 electrons are - 1/2.

      Which of the following is not an interstitial compound?
      • a)
        Mn4N
      • b)
        TiC
      • c)
        Fe3H
      • d)
        FeCl3
      Correct answer is option 'D'. Can you explain this answer?

      Lavanya Menon answered
      The correct answer is option D
      An interstitial compound is a compound that is formed when an atom with a small enough radius sits a hole in a metal lattice
      They are usually transitional elements
      Eg: Tic, Mn4N, Fe3H, TiH2 etc.
      Main Characteristics:-
      ·        High melting points than metals
      ·        They are much harder
      ·        They become chemically inert
      ·        They become less malleable
      So, the answer is (a), (b), (c) .
       

      What is the most common oxidation state for actinoids?
      • a)
        +3
      • b)
        +7
      • c)
        +2
      • d)
        +5
      Correct answer is option 'A'. Can you explain this answer?

      Mamali . answered
      Unlike lanthanides which show the +3, oxidation States,actinides show a variety of Oxidation State from +3to+6.However+3&+4 are the principal Oxidation State.The+3 Oxidation state is the most stable in AC and all the other elements of the series.Thats it.

       In neutral solution, potassium permanganate forms:
      • a)
        Manganese dioxide
      • b)
        Manganous sulphate
      • c)
        Pyrolusite
      • d)
        Potassium manganite
      Correct answer is option 'A'. Can you explain this answer?

      Prakash answered
      KMno₄ is an oxidising agent (here Mn⁺⁷)in nuetral medium there is a change of 3 in it's oxidation state M⁺⁷-------Mn⁺⁴

      The actinoids exhibits more number of oxidation states in general than the lanthanoids. This is because  
      [AIEEE-07]
      • a)
        The 5f-orbitals are more buried than the 4f-orbitals
      • b)
        There is a similarly between 4f-and-5f in the their angular part of the wave function
      • c)
        The actinoids are more reactive than the lanthanoids
      • d)
        The 5f-orbitals extend further from the nucleus than the 4f-orbitals
      Correct answer is option 'D'. Can you explain this answer?

      T.ttttt answered
      Lanthanoids primarily show three oxidation states (+2, +3, +4). Among these oxidation states, +3 state is the most common. Lanthanoids display a limited number of oxidation states because the energy difference between 4f, 5d and 6s orbitals is quite large. On the other hand, the energy difference between 5f, 6d and 7s orbitals is very less. Hence, actinoids display a large number of oxidation states.

      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.

      The elements which lie between s and p block elements in the long form periodic table are called as:
      • a)
        Actinides
      • b)
        d-block elements
      • c)
        Lanthanides
      • d)
        Electropositive elements
      Correct answer is option 'B'. Can you explain this answer?

      Harsh Desai answered
      D-block elements

      The long form periodic table consists of four blocks: s, p, d, and f. The s and p blocks are located on the left and right sides of the periodic table, respectively. The d-block elements are located in the middle of the periodic table, between the s and p blocks. These elements are also known as transition elements.

      Explanation:

      The d-block elements are characterized by the presence of partially filled d-orbitals in their valence shells. These elements are often referred to as transition elements because they exhibit a transition between the highly reactive s-block elements and the relatively inert p-block elements. The d-block elements are known for their unique chemical and physical properties, such as their ability to form complex ions and their high melting and boiling points.

      Examples of d-block elements include titanium, iron, copper, and zinc. These elements are widely used in industry and technology due to their unique properties, such as their strength, durability, and conductivity.

      In summary, the elements which lie between s and p block elements in the long form periodic table are called d-block elements or transition elements. These elements exhibit unique chemical and physical properties and are widely used in industry and technology.

       Brass is an alloy of:
      • a)
        Copper and molybdenum
      • b)
        Copper and zinc
      • c)
        Copper and tungsten
      • d)
        Copper and tin
      Correct answer is option 'B'. Can you explain this answer?

      Krishna Iyer answered
      Brass is an alloy of copper and zinc, in proportions which can be varied to achieve varying mechanical and electrical properties.It is a substitutional alloy: atoms of the two constituents may replace each other within the same crystal structure.
      Brass is similar to bronze, another alloy containing copper that uses tin in place of zinc; both bronze and brass may include small proportions of a range of other elements including arsenic, lead, phosphorus, aluminum, manganese, and silicon.

      Which one is of the following is the lightest transition element?
      • a)
        Ti 
      • b)
        Sc 
      • c)
        Fe 
      • d)
        Hg
      Correct answer is option 'B'. Can you explain this answer?

      T.ttttt answered
      Scandium (Sc) is the lightest transition element. It is the first element in the 3d transition series. Among the transition elements, Sc has the lowest density.

      Cerium (Z = 58) is an important member of the lanthanoids. Which of the following statement about cerium is incorrect -
      [AIEEE-04]
      • a)
        Cerium (IV) acts as an oxidising agent
      • b)
        The +3 oxidation state of cerium is more stable than the +4 oxidation state
      • c)
        The +4 oxidation state of cerium is not known in solutions
      • d)
         The common oxidation states of cerium are +3 and +4
      Correct answer is option 'C'. Can you explain this answer?

      Ritu Singh answered
      The incorrect statement about the Cerium is only a C option.
      C: The +4 oxidation state of cerium is not known in solutions [ Incorrect ]
      As +4 oxidation state is common for the Cerium.
      The correct statement about the Cerium are as follows:
      A: The common oxidation states of Cerium are +3, and +4.
      B : The +3 oxidation state of the Cerium is more stable than the +4 oxidation state.
      D: Cerium (IV) acts as an oxidising agent

      If molarity of K2Cr2O7 solution is 0.5 M, its normality value is
        Correct answer is '3'. Can you explain this answer?

        Ishani Patel answered
        Normality = molarity x number of electrons gained per mole of dichromate in a redox reaction. Hence, Normality = Molarity x 6

        Which one of the following is a diamagnetic ion?
        • a)
          CO2+
        • b)
          Cu2+
        • c)
          Mn2+
        • d)
          Sc3+
        Correct answer is option 'D'. Can you explain this answer?

        Ameya Pillai answered
        Co2+ (Z = 27) : [Ar]183d7 (3 unpaired electrons)
        Cu2+ (Z = 29) : [Ar]183d9 (1 unpaired electrons)
        Mn2+ (Z = 25): [Ar]183d5 (5 unpaired electrons)
        Sc3+ (Z = 21): [Ar]183d0 (No unpaired electron)
        Sc3+ with no unpaired electron will be diamagnetic

         Excess of KI reacts with CuSO4 solution and then Na2S2Osolution is added to it. Which of the statements is incorrect for this reaction -
        [AIEEE-04]
        • a)
          Evolved I2 is reduced
        • b)
          CuI2 is formed 
        • c)
          Na2S2Ois oxidised
        • d)
          Cu2I2 is formed
        Correct answer is option 'B'. Can you explain this answer?

        Swati Verma answered
        The correct answer is option B
        It is given that an excess of KI reacts with CuSO4​ solution and then Na2​S2​O3​ is added to it. This is hypo test and reactions are as follows:
        2CuSO4​ + 4KI → 2K2​SO4 ​+ 2CuI+I2
        2Na2​S2​O3​ + I2​→ Na2​S4​O6 ​+ 2NaI
        CuI2​ is not formed according to the following reaction.
        2CuI2​(unstable) → 2CuI+I2
        Hence, the statement in option B is incorrect.
         

        The colourless ions among the lanthanides are
        • a)
          La3+
        • b)
          Gd3+
        • c)
          Lu3+
        • d)
          Ce3+
        Correct answer is option 'A,B,C,D'. Can you explain this answer?

        La3+, Gd3+ and Lu3+ have empty (4f0) half-filled (4f7) and full-filled (4f14) orbitals. Ce3+ (4f1) is colourless because it does not absorb in the visible region.

        During the process of electrolytic refining of copper, some metals present as impurity settle as ‘anode mud’ These are
        • a)
          Sn and Ag
        • b)
          Pb and Zn
        • c)
          Ag and Au
        • d)
          Fe and Ni
        Correct answer is option 'C'. Can you explain this answer?

        Hansa Sharma answered
        The correct answer is option C
        In Electrolytic refining, the impure metal is made to act as an anode. A strip of the same metal in pure form is used as a cathode. 
        They are put in a suitable electrolytic bath containing a soluble salt of the same metal. 
        The more basic metal remains in the solution and the less basic ones go to the anode mud.
        Copper is refined using an electrolytic method.
        Impurities from the blister copper deposit as anode mud which contains antimony, selenium, tellurium, silver, gold, and platinum; recovery of these elements may meet the cost of refining.

        In which of the following oxidation state Cerium achieves the noble gas configuration?
        • a)
          +5
        • b)
          +2
        • c)
          +7
        • d)
          +4
        Correct answer is option 'D'. Can you explain this answer?

        Mamali . answered
        The reason for this behaviour is a result of the stability of half filled, empty or fulfilled F orbitals that these elements achieve in these Oxidation State.Thats it.

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