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8.38 What can be inferred from the magnetic moment values of the following complex species ?

Example                                    Magnetic Moment (BM)

K_{4}[Mn(CN)_{6})                                2.2

[Fe(H_{2}O)_{6}]^{2+}                                          5.3

K_{2}[MnCl_{4}]                                            5.9

Magnetic moment is given as -  Putting the value on n = 1, 2, 3, 4, 5  (number of unpaired electrons in d-orbital) we get the value of  are 1.732, 2.83, 3.87, 4.899, 5.92 respectively. By comparing with our calculation we get the values n nearest to 1. It means, in above compound d-orbital has one unpaired electron(), which means  is astrong field ligand that cause force pairing of the...

8.37 Comment on the statement that elements of the first transition series possess many properties different from those of heavier transition elements.

Elements of the first transition series possess many properties different from those of heavier transition elements in the following ways- The atomic size of the 1st transition series is smaller than those of 2nd and 3rd series elements. But due to lanthanoid contraction, atomic size of the 2nd series elements are nearly the same as 3rd series element of the corresponding same vertical...

8.36 Write down the number of 3d electrons in each of the following ions: Ti^{2+}, V^{2+}, Cr^{3+}, Mn^{2+}, Fe^{2+}, Fe^{3+}, Co^{2+}, Ni^{2+} and\; \; Cu^{2+}. Indicate how would you expect the five 3d orbitals to be occupied for these hydrated ions (octahedral).

For  d-orvbital has two electron. So, filling of d-orbitals can be  In   d-orbital has three electron. So, the filling of d-orbital can be  Similarily (Ions) (No. of d electrons) (Filling of d-orbitals)

8.35 Compare the general characteristics of the first series of the transition metals with those of the second and third series metals in the respective vertical columns. Give special emphasis on the following points:

(iv) atomic sizes.

 

Generally, atomic sizes decrease from left to right across the period. In among the three transition series, the size of the second series element is bigger than that of the first transition element of the same vertical group. But the atomic size of the third transition element is nearly the same as the element of the second transition series element. This is because of Lanthanoid contraction.

8.35 Compare the general characteristics of the first series of the transition metalswith those of the second and third series metals in the respective vertical columns. Give special emphasis on the following points:

(iii) ionisation enthalpies

In all of the three transition series, the 1st ionisation energy increases from the left side to right side. But, there are some exceptions like the first ionisation enthalpies of the third transition series are more significant than those of the first and second transition series. This is happening due to the weak shielding effect of 4 electrons in the third series. Some elements in the...

8.35 Compare the general characteristics of the first series of the transition metalswith those of the second and third series metals in the respective vertical columns. Give special emphasis on the following points:

(ii) oxidation states

In each of the three transition series, the no. of oxidation state is minimum at the extremes and the highest at the middle of the row. In the first transition series, the +2 and +3 oxidation state are quite stable. Elements of first transition series metals form stable compounds of +2 and +3 oxidation state. But the stability of +2 and +3 oxidation state decreases in second and third...

8.35 Compare the general characteristics of the first series of the transition metals with those of the second and third series metals in the respective vertical columns. Give special emphasis on the following points:

(i) electronic configurations

Electronic configurations- In 1st, 2nd and 3rd transition metal series 3, 4 and 5 orbitals are used respectively. In first series copper and zinc show unusual electronic configuration.  In the second transition series different electron configuration shown by following metals,  (42) = 4d5 5s1, (43) = 4d6 5s1, (44) = 4d7 5s1, (45) = 4d8 5s1, (46) = 4d10 5s0, (47) = 4d10 5s1 In 3rd series there...

8.34 Write the electronic configurations of the elements with the atomic numbers 61, 91, 101, and 109.

Atomic number = 61, Promethium the electronic configuration is  atomic number = 91, protactinium the electronic configuration is  Atomic number = 101, Mendelevium the electronic configuration is  Atomic number = 109, Meitnerium the electronic configuration is 

8.32 Name the members of the lanthanoid series which exhibit +4 oxidation states and those which exhibit +2 oxidation states. Try to correlate this type of behaviour with the electronic configurations of these elements.

Members of the lanthanoids which exhibits +4 oxidation states are-  members who exhibit +2 oxidation states =  After losing 4 electrons attains stable configuration  and also the same thing happen to  In the case of  and ,  after losing two electrons they also get their stable electronic configuration.  

8.31 Use Hund’s rule to derive the electronic configuration of Ce^{3+} ion, and calculate its magnetic moment on the basis of ‘spin-only’ formula.

Electronic configuration of Magnetic moment can be calculated as , where n= no. of unpaired electrons in Cerium n = 2 So, by putting the value of n we get  

8.30 Which is the last element in the series of the actinoids? Write the electronic configuration of this element. Comment on the possible oxidation state of this element.

 

The last element of the actinoid series is Lawrencium (). Its atomic number is 103. The electronic configuration of  is . The possible oxidation state of lawrencium is +3 because after losing 3 electrons it becomes a stable molecule.

8.29 The chemistry of the actinoid elements is not so smooth as that of the lanthanoids. Justify this statement by giving some examples from the oxidation state of these elements.

 

Lanthanoid primarily shows three oxidation states +2, +3, and +4 and out of these +3 is most common in lanthanoids. they show limited no. of oxidation states due to the large difference in energies of 4, 5 and 6 orbitals. But, actinoids shows large no. of oxidation state because they have comparable energy difference in 5,6 and 7 orbitals. For example  and  exhibits +3, +4, +5 and +6 oxidation states.

8.28 What are inner transition elements? Decide which of the following atomic numbers are the atomic numbers of the inner transition elements : 29, 59, 74, 95, 102, 104.

Inner transition metals are those in which the last electrons are filled in f-orbitals. The elements in which 4f and 5f are filled are called f block elements. 59, 95 and 102 are the inner transition elements.

8.27 What are alloys? Name an important alloy which contains some of the lanthanoid metals. Mention its uses.

It is a solid solution of two or more elements in a metallic matrix. Alloys possess different physical properties than component materials. An important alloy of lanthanoid is mischmetal. uses- mischmetal is used in cigarettes and gas lighters Used in flame-throwing tanks It is used in tracer bullets and shells

8.26 Indicate the steps in the preparation of:

(ii) KMnO_{4} from pyrolusite ore.

Potassium permanganate can be prepared from the fusion of pyrolusite ore() with an alkali metal hydroxide and an oxidising agent (like ). This gives dark green . It disproportionates in acidic or neutral medium to give permanganate.

8.26 Indicate the steps in the preparation of:

(i) K_{2}Cr_{2}O_{7}  from chromite ore.

(i) Potassium dichromate is obtained from the fusion of chromite ore  with sodium and potassium carbonate in the free supply of air. (ii) Sodium chromate is filtered and acidified with sulphuric acid () to form sodium dichromate,  can be crystallised (iii) Sodium dichromate is more soluble than potassium dichromate. So, treat the solution of dichromate with the potassium chloride() The...

8.25 Give examples and suggest reasons for the following feature of the transition metal chemistry:

(iii) The highest oxidation state is exhibited in oxoanions of a metal.

Oxygen is a strong oxidizing agent because of its small in size and high electronegativity. Thus oxo-anions of metals shows the highest oxidation state. For example- , here manganese shows +4 oxidation state.

8.25 Give examples and suggest reasons for the following feature of the transition metal chemistry:

(ii) A transition metal exhibits highest oxidation state in oxides and fluorides.
 

Oxygen and fluorine are a strong oxidizing agent because of their small in size and high electronegativity. So, they help transition metals to exhibit the highest oxidation states. Examples of oxides and fluorides of transition metals are  and 

8.25 Give examples and suggest reasons for the following feature of the transition metal chemistry:

(i) The lowest oxide of transition metal is basic, the highest is amphoteric/acidic.
 

The lowest oxidation states of transition metals are basic because some of their valence electrons are not participating in bonding. Thus they have free electrons, which they can donate and act as a base. In the higher oxide of transition metals, valence electron of their participate in bonding, so they are unavailable. But they can accept electrons and behave as an acid. For example (+2)-...

8.24 Which one of these is the most stable in aqueous solution?

\\(i)Mn^{3+}\\(ii)Cr^{3+}\\(iii)V^{3+}\\(iv)Ti^{3+}

 

is the most stable in the aqueous solution solution because it attains the configuration, which is stable configurtaion. Eelectronic configuration of  = 
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