Tag: the d-and f-block elements

Questions Related to the d-and f-block elements

Find the solid which has brilliant blue color.
  1. $Fe _2O _3$

  2. $CuSO _4$

  3. $NaBr$

  4. $KCl$

  5. $Ca(OH) _2$


Correct Option: B
Explanation:

Copper sulphate $\displaystyle CuSO _4$ has brilliant blue color.
$Cu(II)$ ions with an outer electronic configuration of  $\displaystyle 3d^{9}$ have one unpaired electron. This results in blue colour which is due to $d-d$ transitions.

Which of the following is not an actinoid?

  1. Curium (Z = 96)

  2. Californium (Z = 98)

  3. Uranium (Z = 92)

  4. Terbium (Z = 65)


Correct Option: D
Explanation:

Terbium (Z = 65) is a lanthanoid and all others are actinoids. Lanthanoids have atomic numbers from 58 to 71. Actinoids have atomic numbers from 90 to 103.

Identify the incorrect statement among the following. 

  1. 4f and 5f orbitals are equally shielded.

  2. 4-Block elements show irregular and erratic chemical properties among themselves.

  3. La and Lu have partially filled d-orbitals and no other partially filled orbitals.

  4. The chemistry of various lanthanoids is very similar.


Correct Option: A
Explanation:

4f and 5f orbitals are not equally shielded. 5f are poorly shielded as 5f orbitals are away from the nucleus.

Also, 5f has poor shielding effect than 4f due to the large size of f-orbital, it is more diffused.

Which of the following is not an actinoid ?

  1. Am

  2. Cm

  3. Fm

  4. Tm


Correct Option: D
Explanation:

LANTHANIDES


58Ce  59Pr  60Nd  61Pm  62Sm  63Eu  64Gd  65Tb  66Dy  67Ho  68Er  69Tm  70Yb  71Lu 

ACTINIDES

 90Th 91 Pa 92 U 93 Np 94 Pu 95 Am 96 Cm 97Bk  98Cf  99Es  100 Fm 101 Md 102No  103Lr 
          

Which of the following is not an actinide ?

  1. Curium

  2. Californium

  3. Uranium

  4. Terbium


Correct Option: D
Explanation:

LANTHANIDES


58Ce  59Pr  60Nd  61Pm  62Sm  63Eu  64Gd  65Tb  66Dy  67Ho  68Er  69Tm  70Yb  71Lu 

ACTINIDES

 90Th 91 Pa 92 U 93 Np 94 Pu 95 Am 96 Cm 97Bk  98Cf  99Es  100 Fm 101 Md 102No  103Lr 
          

Which of the following elements belongs to actinide series?

  1. Lu

  2. Gd

  3. Th

  4. La


Correct Option: C
Explanation:

Lu, Gd and La belongs to lanthanide series and Th belongs to actinide series.


Option C is correct.

The first and last elements of actinides are:

  1. Actinium and Thorium

  2. Actinium and Nobelium

  3. Actinium and Mendelevium

  4. Actinium and Lawrencium


Correct Option: D
Explanation:

We have 15 elements in actinides. They are from atomic number 89 to 103 Actinium, Thorium, Protactinium, Uranium, Neptunium, Plutonium, Americium, Curium, Berkelium, Californium, Einsteinium, Fermium, Mendelevium, Nobelium, Lawrencium. Hence, from these list we could say that Actinium is the first and Lawrencium is the last element in actinides.

5f series elements are known as_______

  1. Lanthanides

  2. Representative elements

  3. Transition elements

  4. Actinides


Correct Option: D
Explanation:

Actinides are also called the 5f series.


 Filling up of the 5f orbitals after actinium (Z = 89) gives the 5f-inner transition series known as the actinoid series.

Option D is correct.

Actiniod contraction is more than lanthanold contraction because:

  1. energy of 4f and 5f orbitals are same

  2. 5f orbitals are more diffused as compared to 4f orbitals

  3. actinoids show greater range of oxidation states than lanthanoids

  4. actinoids are highly reactive


Correct Option: B
Explanation:

$5f$ orbitals are bigger than $4f$ orbitals, in other words, $5f$ orbitals are more diffused thereby having the poor shielding effect. Hence have a more effective nuclear charge thereby having a small size. Hence actinide contraction is more than lanthanide contraction.

Assertion 


The degree of complex formation in actinides decreases in the order:

     $ \ M^{4+}>MO^{2+} _{2}> M^{3+}>MO^{+} _{2} $

Reason

Actinides form complexes with $\pi $ bonding ligands such as alkyl phosphines and thioethers.

  1. Both Assertion and Reason are correct and Reason is correct explanation for Assertion.

  2. Both Assertion and Reason are correct and Reason is not correct explanation for Assertion

  3. Both Assertion is correct but Reason incorrect.

  4. Both Assertion and Reason are incorrect


Correct Option: B