ECAT MCQs

Effective nuclear charge generally increases across a period.
Electrons are therefore harder to remove, with some exceptions.

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

Valence electrons are farther from the nucleus and more shielded down a group.
They are generally easier to remove.

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

Forming Na+ removes the outer 3s electron.
The cation is smaller than the neutral atom.

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

Adding an electron increases electron-electron repulsion.
The anion is larger than the neutral atom.

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

Ionic bonding follows electron transfer and ion formation.
The resulting cations and anions attract in a lattice.

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

Covalent bonds commonly form between nonmetal atoms.
Shared electrons are attracted to both nuclei.

First ionization energy removes the first electron from a neutral gaseous atom.
Successive ionization energies remove additional electrons.