Karnataka Board PUCPUC Science 2nd PUC Class 12

Zr and Hf have almost similar atomic radii - Chemistry


Account for the following :

Zr and Hf have almost similar atomic radii.



Due to lanthanide contraction, Zr and Hf have almost similar atomic radii. It can be explained on the basis of shielding effect. The electrons present in inner shells, shield the outer electrons from nuclear charge, making them experience a low effective nuclear charge. The shielding effect exerted by the electrons decreases in the order s > p > d > f. The f subshell poorly shields the outer electrons from nuclear attraction, which results in more attractive pull of nucleus on outer electron. In case of post lanthanide elements like Hf, 4f subshell is filled and it is not very effective at shielding the outer shell electrons. Therefore, Zr and Hf have almost similar atomic radii.

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2014-2015 (March) Patna Set 2


Define lanthanoid contraction.

What are chemical twins? Write ‘two’ examples.

What are lanthanoids?

Which among the following pairs of elements is 'not' an example of chemical twins?

Name a member of the lanthanoid series which is well known to exhibit +4 oxidation state.

What are the different oxidation states exhibited by the lanthanoids?

Compare the chemistry of actinoids with that of the lanthanoids with special reference  to electronic configuration

Compare the chemistry of actinoids with that of the lanthanoids with special reference to atomic and ionic sizes

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.

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

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

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

Write the different oxidation states of iron

What is lanthanoid contraction?

Explain, why lanthanum (Z = 57) forms La3+ ion, while cerium (Z = 58) forms Ce4+ ion?

Explain effects of lanthanoid contraction

What are the consequences of lanthanoid contraction?

Explain the cause of lanthanoid contraction?

What is Lanthanoid contraction?

Explain the cause of Lanthanoids contraction.

Answer the followiiig questions: 
Which trivalent ion has maximum size in the Lanthanoid series i.e. Lanthanum ion (La3+) to Luteium ion (Lu3+)? 
(at. no. of Lanthanum  = 57 and Lutetium = 71) 

What is meant by Lanthanide contraction? Write the general electronic configuration of inner transition elements. 

What is the action of the following on lanthanoids?
a. water
b. Sulphur, heat
c. nitrogen, heat

Gadolinium belongs to 4f series. It’s atomic number is 64. Which of the following is the correct electronic configuration of gadolinium?

General electronic configuration of actinoids is `(n-2)f^(1-14)(n - 1)d^(0-2)ns^2`.Which of the following actinoids have one electron in 6d orbital?

(i) U (Atomic no. 92)

(ii) Np (Atomic no.93)

(iii) Pu (Atomic no. 94)

(iv) Am (Atomic no. 95)

Which of the following lanthanoids show +2 oxidation state besides the characteristic oxidation state +3 of lanthanoids?

(i) \[\ce{Ce}\]

(ii) \[\ce{Eu}\]

(iii) \[\ce{Yb}\]

(iv) \[\ce{Ho}\]

Match the compounds/elements given in Column I with uses given in Column II.

  Column I (Compound/element) Column II (Use)
(i)  Lanthanoid oxide (a) Production of iron alloy
(ii)  Lanthanoid (b) Television screen
(iii)  Misch metal (c) Petroleum cracking
(iv)  Magnesium based alloy is constituent of (d) Lanthanoid metal + iron
(v)  Mixed oxides of lanthanoids are employed (e) Bullets
    (f) In X-ray screen

On the basis of Lanthanoid contraction, explain the following:

Radii of 4d and 5d block elements.

How would you account for the following:

There is a greater range of oxidation states among the actinoids than among the lanthanides.

Which of the following pairs has the same ionic size?

The titanium (Z = 22) compound that does not exist is:-

In lanthanoid the last electron enters (n - 2)f subshell where n is equal to ______.

Zr(Z = 40) and Hf(Z = 72) have similar atomic and ionic radii because of ______ 

Zr (Z = 40) and Hf (Z = 72) have similar atomic and ionic radii because of ______.

Zr (Z = 40) and Hf (Z = 72) have similar atomic and ionic radii because of _______.

The lathanide ion that would show colour is ______.

Which one of the lanthanoids given below is the most stable in divalent form?

Mischmetal is an alloy consisting mainly of ______.

Cerium (Z = S8) is an important member of lanthanoids. Which of the following statements about cerium is incorrect?

Write a note on lanthanoids.

State a reason for the following:

La(OH)3 is more basic than Lu(OH)3.


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