Question

what must be true for an energy level diagram to be correct? (choose all that apply.) lowest energy orbitals are filled first. each orbital contains two electrons of opposite spin. all electrons must be pointing the same way. the principal quantum numbers must be filled in order. 25 multiple choice 1 point alkali metals are the most reactive elements on the periodic table because... they have the highest ionization energies. they have the highest electron affinities. they have the lowest ionization energies. they have the lowest electron affinities.

Explanation:

First Question (Energy Level Diagram)

• For "Lowest energy orbitals are filled first": Follows the Aufbau principle, so this is true.
• For "Each orbital contains two electrons of opposite spin": Follows Pauli exclusion principle, so this is true.
• For "All electrons must be pointing the same way": Violates Hund's rule and Pauli principle (electrons in same subshell have parallel spins first, and opposite in same orbital), so false.
• For "The principal quantum numbers must be filled in order": Not strictly true (e.g., 4s fills before 3d), so false.

Alkali metals have one valence electron. Ionization energy is the energy to remove an electron. Lower ionization energy means easier to lose the valence electron, increasing reactivity. Highest ionization energy would make losing electrons hard (less reactive). Electron affinity is about gaining electrons; alkali metals don't gain easily. Lowest electron affinity isn't the reason for high reactivity (reactivity here is about losing electrons). So they have the lowest ionization energies.

Answer:

• Lowest energy orbitals are filled first.
• Each orbital contains two electrons of opposite spin.

Question 25 (Alkali Metals Reactivity)