"More intensity = more KE in photoelectric effect" WRONG. Intensity = photon count. KE = h(ν−ν_{0}) depends on frequency ONLY.

"Electron orbit = orbital" WRONG. Orbit (Bohr) = fixed circular path. Orbital (QM) = 3D region of probability (90% boundary).

"All s orbitals are identical in shape" WRONG. All s orbitals are spherical, but they differ in size (r ∝ $n^{2}$) and number of radial nodes.

"Energy increases as n increases in Bohr model" PARTIALLY MISLEADING. Energy becomes LESS NEGATIVE (increases toward 0). The electron is less tightly bound but more energetic in terms of the number value.

"l=n is possible for l values" WRONG. l ranges 0 to (n−1). l CANNOT equal n. For n=2, l_max = 1 (p), NOT 2 (d).

"Spectral lines from n levels = n" WRONG. Lines = n(n-1)/2. From n=4: 6 lines, NOT 4.

"4s is higher energy than 3d always" WRONG for neutral atoms: 4s fills before 3d (lower energy in neutral). BUT for cations, 4s is higher energy and empties first.

"Cr has [Ar] 3$d^{4}$ 4$s^{2}$" WRONG. Cr = [Ar] 3$d^{5}$ 4$s^{1}$ due to half-filled stability.

"Cu has [Ar] 3$d^{9}$ 4$s^{2}$" WRONG. Cu = [Ar] 3$d^{10}$ 4$s^{1}$ due to fully-filled d stability.

"de Broglie wavelength applies only to electrons" WRONG. λ = h/mv applies to ALL matter (electrons, protons, photons, baseballs). For large masses, λ is negligibly small.

"Nodes are regions of maximum electron density" WRONG. Nodes are exactly the OPPOSITE — regions where electron probability = ZERO.

"mₗ can be any integer value" WRONG. mₗ ranges from −l to +l. For l=2: mₗ = {−2, −1, 0, +1, +2} ONLY (5 values).

"Heisenberg principle means we cannot measure simultaneously" WRONG (nuance). It is not an instrument limitation. It is a fundamental quantum property — the electron DOES NOT HAVE simultaneously definite position and momentum.

"The 3d and 4s fill in order 3d first, then 4s" WRONG. By Aufbau (n+l rule): 4s (n+l=4) fills before 3d (n+l=5).

"The energy of an electron depends on n, l, mₗ, mₛ" WRONG for hydrogen-like atoms. In one-electron species, energy depends ONLY on n.

"$Fe^{2+}$ loses 3d electrons to form from Fe" WRONG. Fe: [Ar]3$d^{6}$4$s^{2}$. $Fe^{2+}$ loses the two 4s electrons → [Ar]3$d^{6}$. Always remove 4s before 3d.