Periodic Table and Periodicity AFCAT Questions

AFCAT Chemistry

Periodic Table and Periodicity MCQ Questions


13.
Why is the second ionization enthalpy always greater than the first?
A.
Because of decrease in atomic radius after first ionization only
B.
Because removing an electron from a positively charged ion is more difficult than from a neutral atom
C.
Because the second electron is removed from a different shell
D.
Because the nuclear charge decreases after first ionization
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ANSWER :
B. Because removing an electron from a positively charged ion is more difficult than from a neutral atom
14.
The first ionization enthalpy of B is less than that of Be because:
A.
B is more electronegative than Be
B.
Be has half-filled stable configuration
C.
The 2p electron of B is more shielded and at higher energy than the 2s electron of Be
D.
B has more electrons than Be
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ANSWER :
C. The 2p electron of B is more shielded and at higher energy than the 2s electron of Be
15.
The first ionization enthalpy of oxygen is less than that of nitrogen because:
A.
Oxygen has higher atomic number
B.
Nitrogen has half-filled stable 2p³ configuration; in oxygen, two electrons in same 2p orbital cause repulsion, easing electron removal
C.
Oxygen has more shielding effect
D.
Oxygen has smaller size than nitrogen
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ANSWER :
B. Nitrogen has half-filled stable 2p³ configuration; in oxygen, two electrons in same 2p orbital cause repulsion, easing electron removal
16.
Which element has the highest first ionization enthalpy in the periodic table?
A.
Hydrogen
B.
Fluorine
C.
Neon
D.
Helium
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ANSWER :
D. Helium
17.
First ionization enthalpy generally _____ across a period and _____ down a group.
A.
increases; decreases
B.
decreases; decreases
C.
increases; increases
D.
decreases; increases
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ANSWER :
A. increases; decreases
18.
The IE₁ values of group 13 elements are: B(801), Al(577), Ga(579), In(558), Tl(589) kJ/mol. The slight increase from In to Tl is due to:
A.
Poor shielding of nuclear charge by intervening 4f and 5d electrons (lanthanide contraction effect)
B.
Increase in metallic character
C.
Increase in atomic size
D.
Decrease in effective nuclear charge
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ANSWER :
A. Poor shielding of nuclear charge by intervening 4f and 5d electrons (lanthanide contraction effect)