Pakistan MCQs

Noble gases have filled valence shells in their common ground states.
They are generally unreactive.

Increasing nuclear charge pulls electrons closer within the same main shell.
Effective nuclear attraction generally increases across a period.

Additional electron shells are added down a group.
This outweighs the increased nuclear charge.

A d subshell contains five orbitals.
At two electrons per orbital, it holds ten electrons.

The Aufbau principle guides ground-state configurations.
Actual filling order follows orbital energies.

Hund's rule minimizes electron repulsion in degenerate orbitals.
Unpaired electrons have parallel spins before pairing.

The principle limits each orbital to two opposite-spin electrons.
It is fundamental to electron configuration.

Mass number applies to a specific isotope.
It is always a whole number.

The ground state is the most stable configuration.
Energy absorption can promote electrons to excited states.

Isotopes have the same atomic number but different mass numbers.
Their chemical behavior is usually similar.

Excited atoms can return to lower levels by emitting energy.
Atomic spectra arise from these transitions.

Ions form by gaining or losing electrons.
Cations are positive and anions are negative.