=> Ans: The spin-only formula to calculate magnetic moment is: P = √n(n+2) BM
2➤ Write the general electronic configuration of 3d series.
=> Ans: [Ar]3d¹-10 4s²
3➤ Name the radioactive element in lanthanoids.
=> Ans: Promethium (Pm)
4➤ What is lanthanoid contraction?
=> Ans: As we move along the lanthanoid series, there is a decrease in atomic and ionic radii. This steady decrease in the atomic and ionic radii is called lanthanoid contraction.
5➤ Write chemical formula of ore of zinc.
=> Ans: Chemical formula of zinc ore (zink blende): ZnS
6➤ Name the alloy which is formed from copper and tin.
=> Ans: Bronze
7➤ Which alloy is used in the Fischer-Tropsch process in the synthesis of gasoline?
=> Ans: Co-Th alloy is used in the Fischer-Tropsch process in the synthesis of gasoline.
8➤ Name the catalyst used in the hydrogenation of ethene to ethane.
=> Ans: Finely divided Ni
9➤ In which block of the modern periodic table are the transition and inner transition elements placed?
=> Ans. The transition elements are placed in d-block and inner transition elements are placed in f-block of the modern periodic table.
10➤ Write probable electronic configuration of copper?
=> Ans. Copper (Cu) has electronic configuration, 2oCu (Expected): 1s 2s 2p 3s 3p 3d" 4s² (Observed): 18² 25² 2p 3s 3p 3d to 4s¹.
11➤ What is meant by 'shielding of electrons' in an atom?
=> Ans. The inner shell electrons in an atom screen or shield the outermost electron from nuclear attraction. This effect is called shielding effect. The magnitude of shielding effect depends upon the number of inner electrons.
12➤ The atomic number of an element is 90. Is this element diamagnetic or paramagnetic?
=> Ans. The 90th element thorium has electronic configuration, [Rn] 6d27s. Since it has 2 unpaired electrons it is paramagnetic.
13➤ What is hydrometallurgy?
=> Hydrometallurgy: It is a process of extraction of metals. by converting their ores into aqueous solutions of metal compounds and reducing them by suitable reducing agents.
14➤ Cerium and Terbium behave as good oxidising agents in +4 oxidation state. Explain.
=> Ans. (1) The most stable oxidation state of lanthanoids is +3. (2) Hence, Ce (cerium) and Tb (terbium) tend to acquire +3. oxidation state which is more stable. (3) Since they get reduced by accepting electron, they are good oxidising agents in +4 oxidation state. Q. 63. Among the following lathanoids Dy, Gd, Yb, Lu,
15➤ which elements show only one oxidation state 3+ ? Why?
=> Ans. Gd and Lu show only one oxidation state 3+, since they acquire electronic configurations with extra stability namely 4f" and 4f respectively.
16➤ What is meant by lanthanoid contraction?
=> Ans. Lanthanoid contraction: The gradual decrease in atomic and ionic radii of lanthanoids with the increase in atomic number is called lanthanoid contraction.
