CN03 · Quiz — Classification of Elements & Periodicity

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

CN03 — Classification of Elements & Periodicity — Quiz