Account for the following: Zn , Cd , Hg are considered as d-block elements but not as transition elements.

Zinc, cadmium and mercury are not considered as transition elements because of their electronic configuration. The general representation of the electronic configuration of these three elements is n - 1 d 10 ns 2 . The orbitals of these elements are completely filled when they are in their ground state as well as in their general oxidation state. Therefore, these elements are not transition elements.

Account for the following: Chromates change their colour when kept in an acidic solution.

The chromate ion CrO 4 2 - when placed in an acidic medium oxidises and changes to dichromate ion Cr 2 O 7 2 - . Also, the colour of chromate ion changes to orange red from yellow colour. The reaction is: 2 CrO 4 2 - + 2 H + ⇌ Cr 2 O 7 2 - + H 2 O .

Account for the following: Copper (I) compounds are white whereas copper (II) compounds are coloured.

n copper I ion all orbitals are completely filled so its compounds are white and diamagnetic. The electronic configuration of copper II ion is 1s22s22p63s23p63d9 . it has one unpaired electron so it is paramagnetic and forms blue coloured compounds.Read more on Sarthaks.com - https://www.sarthaks.com/379808/copper-compounds-are-white-and-diamagnetic-but-copper-compounds-coloured-paramagnetic n copper I ion all orbitals are completely filled so its compounds are white and diamagnetic. The electronic configuration of copper II ion is 1s22s22p63s23p63d9 . it has one unpaired electron so it is paramagnetic and forms blue coloured compounds.Read more on Sarthaks.com - https://www.sarthaks.com/379808/copper-compounds-are-white-and-diamagnetic-but-copper-compounds-coloured-paramagnetic n copper I ion all orbitals are completely filled so its compounds are white and diamagnetic. The electronic configuration of copper II ion is 1s22s22p63s23p63d9 . it has one unpaired electron so it is paramagnetic and forms blue coloured compounds.Read more on Sarthaks.com - https://www.sarthaks.com/379808/copper-compounds-are-white-and-diamagnetic-but-copper-compounds-coloured-paramagnetic n copper I ion all orbitals are completely filled so its compounds are white and diamagnetic. The electronic configuration of copper II ion is 1s22s22p63s23p63d9 . it has one unpaired electron so it is paramagnetic and forms blue coloured compounds.Read more on Sarthaks.com - https://www.sarthaks.com/379808/copper-compounds-are-white-and-diamagnetic-but-copper-compounds-coloured-paramagnetic In copper (I) ions all the orbitals are completely filled and hence its compounds are white and diamagnetic in nature. One Unpaired electron is present in copper (II) ions and hence they are blue coloured compounds and are paramagnetic in nature. They also show d - d transition.

Give reason and select one atom/ion which will exhibit asked property : Cr or Cu (High melting and boiling point)

Chromium ( Cr ) has a higher melting point because of the half filled stability. Its electronic configuration is 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 1 3 d 5 . Due to the half filled d- orbital, the unpaired electrons forms strong intermetallic bonds hence resulting in high melting point and boiling point. Whereas, the electronic configuration of copper ( Cu ) is 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 9 . It does not have half filled stability.

Give reason and select one atom/ion which will exhibit asked property : Sc 3 + or Cr 3 + (Exhibit diamagnetic behaviour)

Sc 3 + will exhibit diamagnetic behaviour. Electronic configuration of Sc 3 + = 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 Electronic configuration of Cr 3 + = 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 3 Thus, Sc 3 + will exhibit diamagnetic behaviour as it has no unpaired electron.

Give three points of difference between lanthanoids and actinoids.

Lanthanoids Actinoids In lanthanide the filling of 4f orbitals take place. In Actinoids the filling of 5f orbitals take place. Lanthanoids Actinoids These elements are non-radioactive except promethium. All the elements of this series are radioactive. Lanthanoids Actinoids Besides +3 oxidation number it also shows +2 and +4 oxidation state in few compounds. Besides +3 oxidation number it also shows +4,+5 and +7 oxidation state in few compounds.

Calculate the spin only moment of Co 2 + Z = 27 by writing electronic configuration of Co and Co 2 +

The atomic number of cobalt is 27 and the electronic configuration of cobalt is Co = Ar 4 s 2 3 d 7 . Electronic configuration of Co 2 + = Ar 3 d 7 Spin only moment is calculated by using the formula μ = n n + 2 , n = number of unpaired electrons μ = 3 3 + 2 = 3 . 92 B . M

Give reasons: Sc 3 + is a colourless in aqueous solution whereas Ti 3 + is coloured.

Transition metal ions show colour due to the presence of unpaired electrons in d orbital. The atomic number of Sc is 21 and the atomic number of Ti is 22 . The electronic configuration of Sc 3 + = Ar 3 d 0 ⇒ 0 unpaired electron. The electronic configuration of Ti 3 + = Ar 3 d 1 4 s 0 ⇒ 1 unpaired electron Therefore, the aqueous solution of Ti 3 + ion is coloured.

E M B I B E

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR CHEMISTRY>Chapter 8 - The d- and f- Block Elements>CBSE-2019>Q 6

EASY

12th CBSE

IMPORTANT

Earn 100

When ${MnO}_{2}$ is fused with $KOH$ in the presence of ${KNO}_{3}$ as an oxidizing agent, it gives a dark green compound (A). Compound (A) disproportionates in an acidic solution to give a purple compound (B). An alkaline solution of compound (B) oxidises $KI$ to compound (C) whereas an acidified solution of compound (B) oxidises $KI$ to (D). Identify (A), (B), (C) and (D).

Chapter-Wise 3D Chemistry Videos from Embibe Experts EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR CHEMISTRY

08 min 21 sec

The d-block Elements

The periodic table started with elements arranged in increasing order of Z. Now, it can tell us much more about an element. Watch this video to learn more.

05 min 37 sec

The f-block Elements

The elements constituting the f-block are those in which the 4f- and 5f- orbitals are progressively filled. These elements are also known as inner transition...

07 min 39 sec

Oxidation States of Actinoids

The elements in the actinoid group are found to exhibit a large number of oxidation states. This property has contributed to making their chemistry more comp...

Learn and Prepare for any exam you want !

|

|

|

|

|

|

|

|