Classification of Elements and Periodicity in Properties MCQ Questions & Answers in Inorganic Chemistry | Chemistry
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151.
Which of the following represents the correct order of increasing electron gain enthalpy with negative sign for the elements $$O, S, F$$ and $$Cl?$$
A
$$Cl< F< O< S$$
B
$$O< S< F< Cl$$
C
$$F< S< O< Cl$$
D
$$S < O < Cl < F$$
Answer :
$$O< S< F< Cl$$
Key Idea Electron gain enthalpy, generally, increases in a period from left to right and decreases in a group on moving downwards. However, members of $${\text{III}}$$ period have somewhat higher
electron gain enthalpy as compared to the corresponding members of second period, because of their small size.
$$O$$ and $$S$$ belong to $${\text{VI}}\,A\left( {16} \right)$$ group and $$Cl$$ and $$F$$ belong to $${\text{VII}}\,A\left( {17} \right)$$ group. Thus, the electron gain enthalpy of $$Cl$$ and $$F$$ is higher as compared to
$$O$$ and $$S.$$
$$Cl$$ and $$F > O$$ and $$S$$
Between $$Cl$$ and $$F, Cl$$ has higher electron gain enthalpy then the $$F,$$ since the incoming electron experiences a greater force of repulsion because of small size of $$F$$-atom. Similar is true in case of $$O$$ and $$S,$$ i.e. the electron gain enthalpy of $$S$$ is higher as compared to $$O$$ due to its small size. Thus, the
correct order of electron gain enthalpy of given elements is $$O < S < F < Cl$$
152.
Which is the most non-metallic element among the following?
A
$$1{s^2}2{s^2}2{p^6}3{s^1}$$
B
$$1{s^2}2{s^2}2{p^5}$$
C
$$1{s^2}2{s^2}2{p^6}3{s^2}$$
D
$$1{s^2}2{s^2}2{p^3}$$
Answer :
$$1{s^2}2{s^2}2{p^5}$$
It contains maximum number of electrons in the outermost shell. An element with more than 3 electrons in outermost shell is non-metallic.
153.
The correct order of acidic character of oxides in third period of periodic table is
A
$$Si{O_2} < {P_4}{O_{10}} < S{O_3} < C{l_2}{O_7}$$
B
$$C{l_2}{O_7} < S{O_3} < {P_4}{O_{10}} < Si{O_2}$$
C
$$S{O_3} < C{l_2}{O_7} < {P_4}{O_{10}} < Si{O_2}$$
D
$$Si{O_2} < C{l_2}{O_7} < {P_4}{O_{10}} < S{O_3}$$
Acidic character of oxides increases as we move from left to right in a period and depends upon oxidation state of central element.
154.
Consider the following changes
$$A \to {A^ + } + {e^ - }:{E_1}\,{\text{and}}\,{A^ + } \to {A^{2 + }} + {e^ - }:{E_2}$$
The energy required to pull out the two electrons are $${E_1}$$ and $${E_2}$$ respectively. The correct relationship between two energies would be
A
$${E_1} < {E_2}$$
B
$${E_1} = {E_2}$$
C
$${E_1} > {E_2}$$
D
\[{{E}_{1}}\ge {{E}_{2}}\]
Answer :
$${E_1} < {E_2}$$
$$I{E_1}$$ is always less than $$I{E_2}.$$
155.
Consider the following information about element $$P$$ and $$Q:$$
Period number
Group number
$$P$$
2
15
$$Q$$
3
2
A
$$QP$$
B
$${Q_2}{P_3}$$
C
$${Q_3}{P_2}$$
D
$${Q_2}P$$
Answer :
$${Q_3}{P_2}$$
$$P$$ is a trivalent non-metal and $$Q$$ is a divalent metal.
Hence formula of compound is $${Q_3}{P_2}.$$
156.
What is the common property of the oxides $$CO,NO$$ and $${N_2}O?$$
A
All are acidic oxides.
B
All are basic oxides.
C
All are neutral oxides.
D
All are amphoteric oxides.
Answer :
All are neutral oxides.
$$CO,NO$$ and $${N_2}O$$ are natural oxides.
157.
In the long form of periodic table, elements are arranged in the increasing order of
A
atomic mass
B
atomic number
C
mass number
D
metallic character
Answer :
atomic number
No explanation is given for this question. Let's discuss the answer together.
158.
There are two rows of inner transition elements in the periodic table each containing 14 elements. The reason for this may be
A
$$f$$ - orbital has seven values for magnetic quantum number, hence total electrons are 14
B
in the periodic table there is space to accommodate 14 electrons only
C
only 28 inner transition elements have been discovered till date
D
28 is the maximum number of elements that any block can accommodate
Answer :
$$f$$ - orbital has seven values for magnetic quantum number, hence total electrons are 14
For $$f$$ - orbital, $$l = 3,\,{m_l} = 2l + 1 = 7$$
There are 7 electrons with $$ + \frac{1}{2}$$ spin and 7 electrons with $$ - \frac{1}{2}$$ spin. Hence, total electrons are 14.
159.
Which among the following elements has the highest first ionization enthalpy ?
A
Nitrogen
B
Boron
C
Carbon
D
Oxygen
Answer :
Nitrogen
Due to stable $$2{s^2}2{p^3}$$ configuration ( half filled $$p$$ - orbital ). Nitrogen atom has highest energy.
160.
The element with the atomic number 118, will be
A
alkali
B
noble gas
C
lanthanide
D
transition element
Answer :
noble gas
The outermost electronic configuration of element with atomic number 118 is $$7{s^2}7{p^6},$$ so it will be a noble gas.