NDA Chemistry
Classification Elements — Quiz
20 Questions · No Negative Marking
Question 1
Moseley's experiment using X-ray spectra of elements established that the fundamental property of an element is its:
AAtomic mass (Mendeleev's original basis)
BAtomic number Z (number of protons in the nucleus)
CNumber of neutrons in the nucleus
DValence electron configuration
Question 2
The effective nuclear charge (Zeff) increases across a period. Which of the following is the correct Slater's rule for shielding by electrons in the same shell?
AEach electron in the same shell contributes 1.0 to the shielding constant
BEach electron in the same shell contributes 0.35 to the shielding constant
CElectrons in the same shell provide no shielding (contribution = 0)
DEach electron contributes 0.85 to the shielding constant regardless of shell
Question 3
Ionisation energy shows discontinuities within a period. The first ionisation energy of oxygen is LESS than that of nitrogen despite O having higher Z. This is because:
AOxygen has higher atomic mass than nitrogen
BNitrogen has a half-filled 2p subshell
COxygen has more electrons making it harder to ionise
DNitrogen is more electronegative than oxygen
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