General Chemistry: Atomic Structure and Periodic Trends Flashcards

Which quantum number is restricted to values of +½ or −½?

Answer: Spin quantum number (mₛ)

The spin quantum number (mₛ) has only two allowed values — +½ (spin up) or −½ (spin down) — representing the two intrinsic spin states of an electron.

The Pauli Exclusion Principle states that no two electrons in an atom can have:

Answer: The same set of all four quantum numbers

The Pauli Exclusion Principle requires that every electron in an atom has a unique combination of all four quantum numbers (n, l, mₗ, mₛ).

Effective nuclear charge (Zeff) is best described as:

Answer: The net positive charge felt by a valence electron after accounting for electron shielding

Zeff is the actual nuclear attraction experienced by a valence electron, reduced from the full nuclear charge (Z) by the shielding effect of inner-shell electrons.

Which type of electromagnetic radiation carries the highest energy per photon?

Answer: Gamma rays

Gamma rays have the highest frequency and shortest wavelength in the electromagnetic spectrum, giving them the greatest energy per photon (E = hν).

A Period 3 element with a valence configuration of 3s²3p² is:

Answer: Silicon

Silicon (Si, Z = 14) has the electron configuration [Ne]3s²3p², placing it in Period 3 and Group 14 of the periodic table.

Which of the following correctly describes the periodic trend in electronegativity?

Answer: Decreases down a group and increases left to right across a period

Electronegativity decreases down a group (larger atoms, weaker nuclear pull on bonding electrons) and increases left to right across a period (greater nuclear charge).

When an electron in an excited atom transitions from a higher to a lower energy level, the result is:

Answer: Emission of a photon

When an electron falls to a lower energy level, the energy difference is released as an emitted photon whose energy equals hν = ΔE between the two levels.