Tag: chemistry

Questions Related to chemistry

5f series elements are known as_______

chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

  1. Lanthanides

  2. Representative elements

  3. Transition elements

  4. Actinides

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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:

chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

  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

Show answer
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.

chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

  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

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Correct Option: B

Which of the following forms stable oxidation state?

chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

  1. Ce+ , Yb+

  2. Eu + , Tb+

  3. Lu+, Gd

  4. Pr5+ ,Nd2+

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Correct Option: A

Actinoids belongs to following type of elements:

chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

  1. s -block element

  2. d -block element

  3. f -block element

  4. p -block element

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Correct Option: C
Explanation:

The two rows that are generally placed underneath the main Periodic Table are called the lanthanide series and the actinide series.

These two rows are produced when electrons are being added to f orbitals.

Therefore, this block of elements are referred to as the "f block".

Which of the following elements is placed just after actinide series?

chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

  1. Rutherfordium

  2. Unnilpentium

  3. Unnilquadium

  4. Ununbium

Show answer
Correct Option: A,C
Explanation:

Actinide series starts with actinium (Z=89) and contains fourteen elements from thorium (Z=90) to lawrencium (Z=103). This is followed by Rutherfordium (Z=104). There Rutherfordium (Z=104) also known as Unnilquadium.

Hence, both a and c are the correct option.

The bonds generally formin compounds of Actinoids are:

chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

  1. convalent

  2. ionic

  3. coordinate covalent

  4. metallic

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Correct Option: B

Actinide element that exhibits highest oxidation state in its compounds (atomic numbers Th(90), U*, Np(93), Fm(100)

chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

  1. Th

  2. U*

  3. Np

  4. Fm

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Correct Option: B

Which one of the following elements shows maximum number of different oxidation states in its compounds ?

chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

  1. Eu

  2. La

  3. Gd

  4. Am

Show answer
Correct Option: D
Explanation:

Am shows +2, +3, +4, +5, +6, +7 oxidation states.

In the general electronic configuration,
$(n-2)f^{1-14} (n-1)d^{01} ns^2$ (where n = 7) the configuration will be of:

chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

  1. lanthenides

  2. actinides

  3. transition elements

  4. none

Show answer
Correct Option: B
Explanation:

General electronic configuration is given:
$(n -2) f^{1 -14} (n -1) d^{0 1} ns^2 ,where ( n =7 )$
$5f^{1 -14} 6d^{0 1 }ns^2$
The seventh period $(n=7)$ is similar to the sixth period with the successive filling up of the 7s, 5f, 6d and 7p orbitals and includes most of the man-made radioactive elements. This period will end at the element with atomic number 118 which would belong to the noble gas family. Filling up of the 5f orbitals after actinium $(Z=89)$ gives the 5f-inner transition series known as the Actinoid Series.