Classification of Elements and Periodicity in Properties MCQ Questions & Answers in Inorganic Chemistry | Chemistry
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71.
Ionic radii are
A
inversely proportional to effective nuclear charge
B
inversely proportional to square of effective nuclear charge
C
directly proportional to effective nuclear charge
D
directly proportional to square of effective nuclear charge
Answer :
inversely proportional to effective nuclear charge
$${\text{Ionic}}\,{\text{radii}} \propto \frac{1}{{{Z_{eff}}}}$$
$${Z_{eff}} \to $$ effective nuclear charge
This $${{Z_{eff}}}$$ is calculated as follows :
$${Z_{eff}} = Z - $$ screening constant $$\left( \sigma \right)$$
This value of screening constant is based upon the number of electrons in valence shell as well as in penultimate shells.
72.
The correct order of the decreasing ionic radii among the following isoelectronic species is
Key Idea Ionic radii $$ \propto $$ charge on anion $$ \propto \frac{1}{{{\text{charge}}\,{\text{on}}\,{\text{cation}}}}$$
During the formation of a cation, the electrons are lost from the outer shell and the remaining electrons experience a great force of attraction by the nucleus, ie. attracted more towards the nucleus. In other words, nucleus hold the remaining electrons more tightly and this results in decreased radii.
However, in case of anion formation, the addition of electron(s) takes place in the same outer shell, thus the hold of nucleus on the electrons of outer shell decreases and this results in increased ionic radii.
Thus, the correct order of ionic radii is $${S^{2 - }} > C{l^ - } > {K^ + } > C{a^{2 + }}$$
73.
Which pair of elements belongs to same group ?
A
Elements with atomic no. 17 and 38
B
Elements with atomic no. 20 and 40
C
Elements with atomic no. 17 and 53
D
Elements with atomic no. 11 and 33
Answer :
Elements with atomic no. 17 and 53
Atomic no. $$17\left( {Cl} \right)$$ and $$53\left( I \right)$$ are present in the same group
74.
In the long form of periodic table, the non-metals are placed in
A
$$s$$ - block
B
$$p$$ - block
C
$$d$$ - block
D
$$f$$ - block
Answer :
$$p$$ - block
No explanation is given for this question. Let's discuss the answer together.
75.
Which of the following is not an actinoid ?
A
Curium $$\left( {Z = 96} \right)$$
B
Californium $$\left( {Z = 98} \right)$$
C
Uranium $$\left( {Z = 92} \right)$$
D
Terbium $$\left( {Z = 65} \right)$$
Answer :
Terbium $$\left( {Z = 65} \right)$$
Actinoid series : $$_{90}Th$$ to $$_{103}Lr$$
76.
What were the main demerits of Mendeleev's periodic table?
(i) Hydrogen has been placed in group I though it resembles to group VII as well.
(ii) Position of some elements was not justified.
(iii) Isotopes were not given separate places.
(iv) Lanthanides and actinides were not included in the table.
A
(i), (ii) and (iii)
B
(i), (ii), (iii) and (iv)
C
(ii) and (iv)
D
(i), (iii) and (iv)
Answer :
(i), (ii), (iii) and (iv)
No explanation is given for this question. Let's discuss the answer together.
77.
In the periodic table from left to right in a period, the atomic volume
A
decreases
B
increases
C
remains same
D
first decrease then increases
Answer :
first decrease then increases
In the periodic table the atomic size first decreases from left to right in period, so the atomic volume first decreases and then increases because atomic size in last of any period increases.
78.
The correct sequence which shows decreasing order of the ionic radii of the elements is
All the given species contains $$10\,\,\,{e^ - }$$ each i.e.
isoelectronic.
For isoelectronic species anion having high negative charge is largest in size and the cation having high positive charge is smallest.
79.
Atomic radii of fluorine and neon in $$\mathop {\text{A}}\limits^ \circ $$ngstorm units are respectively given by
A
$$0.72,1.60$$
B
$$1.60,1.60\,$$
C
$$0.72,0.72\,\,$$
D
None of these values
Answer :
$$0.72,1.60$$
TIPS/Formulae:
(i) Noble gases do not have covalent radii. They have only vander waal’s radii.
(ii) Covalent radii is always larger than corresponding van-der Waal’s radii.
Atomic radius of neon being van der Waal’s radius is
larger than that of fluorine which is in fact is its covalent radius
80.
Meitnerium is IUPAC official name of an element with atomic number
A
113
B
118
C
104
D
109
Answer :
109
No explanation is given for this question. Let's discuss the answer together.