Chemistry S & P Block Elements MDCAT 2012
PMDC Verified Question 97 of 104
Which one remains same along a period?
A
Atomic radius
B
Number of shells (orbits)
C
Melting point
D
Electrical conductivity
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Number of shells (orbits)
Concept:

A period in the periodic table represents the principal quantum number (n), which corresponds to the outermost electron shell being filled.

Solution:

  • As we move from left to right across a period, electrons are added to the same principal shell.
  • Therefore, the total number of electron shells (orbits) remains constant across a specific period.


Why other options are incorrect:

  • Atomic radius: Decreases across a period due to increasing effective nuclear charge.
  • Melting point: Increases up to Group IVA, then decreases.
  • Electrical conductivity: Decreases as elements transition from metals to non-metals.

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