The d- and f- Block Elements Test

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The d- and f- Block Elements Test - 17

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Weekly Quiz Competition

Question 1
1 / -0

The first IE of lithium is $$5.4$$eV and first electron affinity of $$Cl$$ is $$3.6$$eV. The value of $$\Delta H$$ for the reaction $$Li_{(g)} + Cl_(g) \rightarrow Li^{+}_{(g)} + Cl^{-} _{(g)}$$, is (in eV) :

A
$$+1.8$$

B
$$+ 2.8$$

C
$$- 2.8$$

D
$$+ 9$$

Solution

When lithium becomes a cation we give energy to the system. Hence energy is increased in the system and vice versa for chlorine i.e energy is released.

Hence energy is decreased from the system on the whole energy change is $$5.4-3.6=1.8.$$
Question 2
1 / -0

The first ionisation potential of $$N, P, O$$ and $$S$$ are in the order of:

A
$$S > P < O > N$$

B
$$N > O > P > S$$

C
$$N > O < P > S$$

D
$$N < O < P < S$$

Solution

Moving left to right within a period or upward within a group, the first ionization energy generally increases with a few discrepancies (aluminum and nitrogen group).

Nitrogen group to oxygen group, I.P. decreases instead of increasing because of the stable half-filled configuration of nitrogen family.

$$N(1400) >O(1313)>P(1011)>S(999)$$
Question 3
1 / -0

A reduction in atomic size with increase in atomic number is a characteristic of elements of:

A
d-block

B
f-block

C
radioactive series

D
high atomic masses

Solution

A reduction in atomic size with increase in atomic number is a characteristic of f-block elements.

This is due to poor shielding of f electrons. The extent of actinoid contraction is greater than lanthanoid contraction.

With increase in atomic number i.e. in moving down a group, the number of the principal shell increases and therefore, the size of the atom increases. But in case of f block elements there is a steady decrease in atomic size with increase in atomic number due to lanthanide contraction. As we move through the lanthanide series, 4f electrons are being added one at each step.

The mutual shielding effect of f electrons is very little. This is due to the shape of the f orbitals. The nuclear charge, however increases by one at each step. Hence, the inward pull experienced by the 4f electrons increases. This causes a reduction in the size of the entire 4fn shell.

Option B is correct.
Question 4
1 / -0

Which of the following ions having the following electronic structure would have a maximum magnetic moment?

A
$$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^23d^{3}$$

B
$$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^23d^{5}$$

C
$$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^23d^{7}$$

D
$$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^23d^{9}$$

Solution

Magnetic moment = $$\sqrt{n(n+2)}$$, where n is no. of unpaired electrons.

Higher the number of unpaired electrons, higher is the magnetic moment.

Number of unpaired electrons are maximum in option B (5 unpaired electrons).

Option A and C: 3 unpaired electrons.

Option D: 1 unpaired electron.
Question 5
1 / -0

Titanium shows the magnetic moment of 1.73 BM. in its compound. What is the oxidation number of $$Ti$$ in the compound?

A
+1

B
+4

C
+3

D
+2

Solution

Magnetic moment = $$\sqrt{n(n+2)}$$ = 1.73 B.M.

$$\therefore$$ Unpaired electrons, $$n$$ = 1

Now, configuration of $$Ti$$ = $$[Ar] 4s^2 3d^2$$.

Hence, the oxidation number must be +3.
Question 6
1 / -0

Which of the following belongs to the actinide series of elements?

A
Y

B
Ta

C
U

D
Lu

Solution

Uranium belongs to actinide series. Yttrium and tantalum belons to d-block. Lutetium belongs to lanthanide series.
Question 7
1 / -0

In the dichromate anion,

A
4 $$Cr-O$$ bonds are equivalent

B
6 $$Cr-O$$ bonds are equivalent

C
all $$Cr-O$$ bonds are equivalent

D
all $$Cr-O$$ bonds are non-equivalent

Solution

In the dichromate anion $$(Cr_2O_7)^{2-}$$, 6 $$Cr-O$$ terminal bonds are equivalent due to resonance.
Question 8
1 / -0

Which of the following belongs to actinoid series of elements?

A
Nd

B
U

C
Sm

D
Au

Solution

Uranium belongs to actinoid series of elements. Neodymium and Samarium belongs to lanthanide series. Gold belongs to d-block.
Question 9
1 / -0

The radius of $$La^{3+}$$ (At. no. of La = 57) is 1.06A. Which one of the following given values will be closest to the radius of $$Lu^{3+}$$? (At. no. of Lu = 71)

A
1.40A

B
1.06A

C
0.85A

D
1.60A

Solution

A reduction in atomic/ionic size with increase in atomic number is a characteristic of lanthanoids. Hence, the ionic radius of $$\displaystyle Lu^{3+}$$ will be smaller than the ionic radius of $$\displaystyle La^{3+}$$. It will be less than 1.06 A. Hence, the option C, 0.85 A is the correct answer.
Question 10
1 / -0

Transition metals are less reactive than alkali metals because they have:

A
high ionisation potential and low melting point

B
high ionisation potential and high melting point

C
low ionisation potential and low melting point

D
low ionisation potential and high melting point

Solution

Transition metals are less reactive than alkali metals because of their high ionization potential and high melting point.

On moving from left to right of the periodic table for every period, electrons fill in the same shell or orbital, with the alkali metals having the least filled outermost shells, one electron, which equates to fewer protons in them.

Consequently, they have a lesser attraction power from the nucleus, whereas, the corresponding transition metals of the same period have more protons interacting with electrons at the same distance, far from the nucleus as the alkali metals.

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Re-Attempt Weekly Quiz Competition

The d- and f- Block Elements Test - 17

Result

The d- and f- Block Elements Test - 17

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Question 1

$$+1.8$$

$$+ 2.8$$

$$- 2.8$$

$$+ 9$$

Solution

Question 2

$$S > P < O > N$$

$$N > O > P > S$$

$$N > O < P > S$$

$$N < O < P < S$$

Solution

Question 3

d-block

f-block

radioactive series

high atomic masses

Solution

Question 4

$$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^23d^{3}$$

$$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^23d^{5}$$

$$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^23d^{7}$$

$$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^23d^{9}$$

Solution

Question 5

+1

+4

+3

+2

Solution

Question 6

Y

Ta

U

Lu

Solution

Question 7

4 $$Cr-O$$ bonds are equivalent

6 $$Cr-O$$ bonds are equivalent

all $$Cr-O$$ bonds are equivalent

all $$Cr-O$$ bonds are non-equivalent

Solution

Question 8

Nd

U

Sm

Au

Solution

Question 9

1.40A

1.06A

0.85A

1.60A

Solution

Question 10

high ionisation potential and low melting point

high ionisation potential and high melting point

low ionisation potential and low melting point

low ionisation potential and high melting point

Solution

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