Chapter 1

Question 1

What is the Atomic Number (Z)?

Answer 1

Number of protons in nucleus (defines element).

Equals number of electrons in a neutral atom. Appears as the smaller whole number on periodic‑table tile (e.g., K = 19).

Question 2

What is the Mass Number (A)?

Answer 2

Total protons + neutrons in a single isotope.

Written as left superscript in nuclide notation (e.g., ¹⁴C). Approximates atomic mass in amu because electrons are negligible in mass.

Question 3

What is Atomic Weight?

Answer 3

Weighted average of all natural isotopes’ masses.

Same numerical value (but units differ) for: amu per atom and g mol⁻¹ per mole. Used to convert between grams ↔ moles with Avogadro’s number.

Question 4

What is an Isotope?

Answer 4

Atoms of same Z(protons) but different A(neutrons)

Nuclide notation: Z A X or X‑A. Chemical behavior similar; nuclear stability & mass differ.

Question 5

What are the charges and masses of subatomic particles?

Answer 5

Proton: +1 e = +1.60 × 10⁻¹⁹ C, ≈ 1 amu, nucleus. Neutron: 0 C, ≈ 1 amu, nucleus. Electron: –1 e = –1.60 × 10⁻¹⁹ C, ≈ 1/2000 amu, orbitals.

Question 6

What is a Cation?

Answer 6

Atom loses e⁻ → positive charge.

Question 7

What is an Anion?

Answer 7

Atom gains e⁻ → negative charge.

Question 8

What is Avogadro’s Number (N_A)?

Answer 8

6.022 × 10²³ particles per mole (atoms, ions, molecules).

Links microscopic amu scale to macroscopic gram scale.

Question 9

What is Planck’s Constant?

Answer 9

h = 6.626 × 10⁻³⁴ J·s.

Question 10

What is the energy of a photon or quantum?

Answer 10

E = h f.

Higher frequency (f) → higher energy; directly proportional.

Question 11

What is the relationship between photon energy and wavelength?

Answer 11

E = h c / λ.

Energy inversely proportional to wavelength. Combine with E = h f since f = c / λ.

Question 12

What are the key postulates of the Bohr Model?

Answer 12

Electrons travel in fixed circular orbits with quantized angular momentum: L = n h / 2π.

Allowed energies: Eₙ = −R_H / n² (R_H = 2.18 × 10⁻¹⁸ J).

Question 13

What is the Lyman series in hydrogen emission?

Answer 13

Lyman (n ≥ 2 → 1) → UV.

Question 14

What is the Balmer series in hydrogen emission?

Answer 14

Balmer (n ≥ 3 → 2) → visible (≈ 400–700 nm).

Question 15

What is the Paschen series in hydrogen emission?

Answer 15

Paschen (n ≥ 4 → 3) → IR.

Question 16

What does the mnemonic ‘AHED’ represent?

Answer 16

A = Absorb light; H = Higher potential; E = Excited; D = Distant (farther from nucleus).

Question 17

What is the Heisenberg Uncertainty Principle?

Answer 17

Impossible to know exact position & momentum of an electron simultaneously (Δx Δp ≥ ħ/2).

True limit, not equipment flaw; leads to orbital probability clouds.

Question 18

What is the Principal Quantum Number (n)?

Answer 18

Positive integers 1, 2, 3… indicating shell/energy level.

Larger n → larger radius & higher energy. Max electrons per shell = 2n².

Question 19

What does the Azimuthal Quantum Number (l) define?

Answer 19

Defines subshell shape.

l = 0 s, 1 p, 2 d, 3 f. Influences chemical bonding & bond angles.

Question 20

What does the Magnetic Quantum Number (m_l) specify?

Answer 20

Specifies orbital orientation within subshell (e.g., p_x, p_y, p_z).

Each orbital holds max 2 e⁻.

Question 21

What does the Spin Quantum Number (m_s) indicate?

Answer 21

+½ or −½.

Two opposite spins per orbital (Pauli exclusion).

Question 22

What is the Aufbau Principle?

Answer 22

Fill lowest‑energy subshells first.

Question 23

What is the n + l Rule?

Answer 23

Rank by (n + l); lower sum fills first; tie → lower n first.

Explains 4s filling before 3d.

Question 24

What is Hund’s Rule?

Answer 24

Orbitals in same subshell max half‑fill with parallel spins before pairing.

Question 25

What is the Pauli Exclusion Principle?

Answer 25

No two electrons in an atom can have identical values for all four quantum numbers.

Question 26

What is the electron configuration exception for Chromium?

Answer 26

Chromium: [Ar] 4s¹ 3d⁵ (half‑filled d).

Question 27

What is the electron configuration exception for Copper?

Answer 27

Copper: [Ar] 4s¹ 3d¹⁰ (full d).

Question 28

How do you remove electrons for Cations?

Answer 28

Remove from 4s (n = 4) first, then 3d. ## Footnote Example: Fe³⁺ = [Ar] 3d⁵.

Question 29

What is the definition of Paramagnetic?

Answer 29

≥ 1 unpaired e⁻; attracted to magnetic field.

Question 30

What is the definition of Diamagnetic?

Answer 30

All e⁻ paired; repelled.

Question 31

What are the quick rules for Valence Electrons?

Answer 31

Main‑group (s/p‑block): highest n s + n p only. ## Footnote Transition metals: highest n s and same‑row d. Lanthanide/actinide: highest n s + f.

Question 32

What are the shell and subshell capacities?

Answer 32

Shell capacity: 2 n² electrons. ## Footnote Subshell capacity: 4 l + 2 (s=2, p=6, d=10, f=14).

Question 33

How do you calculate protons, neutrons, and electrons for ⁶⁰Ni²⁺?

Answer 33

Z = 28 → 28 protons. A = 60 → neutrons = 60 − 28 = 32. ## Footnote 2+ charge → electrons = 28 − 2 = 26.

Question 34

How do you calculate the photon wavelength for 3 eV energy?

Answer 34

Convert 3 eV → J: 3 × 1.60 × 10⁻¹⁹ = 4.8 × 10⁻¹⁹ J. ## Footnote λ = h c / E = (6.63 × 10⁻³⁴ × 3.00 × 10⁸) / 4.8 × 10⁻¹⁹. λ ≈ 4.1 × 10⁻⁷ m = 410 nm (violet visible).

Question 35

What is the Balmer Series in terms of region and typical colors?

Answer 35

Visible region; lines at 410 nm (violet), 434 nm (blue), 486 nm (cyan), 656 nm (red).

Question 36

What is the electron configuration of Osmium (Z = 76)?

Answer 36

[Xe] 6s² 4f¹⁴ 5d⁶.

Question 37

Which fills first, 5d or 6p?

Answer 37

5d fills first. ## Footnote 5d: n = 5, l = 2 → n+l = 7. 6p: n = 6, l = 1 → n+l = 7 but higher n = 6p higher energy.

Question 38

What are the magnetic properties of Cu⁺ vs Cu²⁺?

Answer 38

Cu⁺: [Ar] 3d¹⁰ → diamagnetic. ## Footnote Cu²⁺: [Ar] 3d⁹ → one unpaired e⁻ → paramagnetic.

Question 39

What is the mnemonic for magnetic behavior?

Answer 39

Paired = Pushes (repelled); Alone = Attracted.

Question 40

What is the combined energy level to photon equation?

Answer 40

ΔE = E_i − E_f = h f = h c / λ = R_H (1/n_f² − 1/n_i²).

Question 41

What is the definition of Ground State?

Answer 41

Electrons occupy lowest possible orbitals (n = 1 for H).

Question 42

What is the definition of Excited State?

Answer 42

≥ 1 electron promoted to higher n; returns by emitting photon.

Question 43

What are the crucial constants to memorize?

Answer 43

h = 6.626 × 10⁻³⁴ J·s. ## Footnote c = 3.00 × 10⁸ m s⁻¹. e = 1.60 × 10⁻¹⁹ C. R_H = 2.18 × 10⁻¹⁸ J. N_A = 6.022 × 10²³ mol⁻¹.

Question 44

What is the explanation for half-filled and fully filled d/f stability?

Answer 44

Electron promotion can occur if resulting subshell is d⁵ or d¹⁰ (or f⁷/f¹⁴). ## Footnote Exchange energy + symmetry lower overall energy; outweighs 4s vacancy.

Question 45

What is an example of a paramagnetic test demonstration?

Answer 45

Liquid O₂ (−183 °C) between magnet poles → bends upward due to unpaired π* electrons.

Question 46

What is the end-of-chapter takeaway?

Answer 46

Master: counting subatomic particles, quantum numbers, n+l ordering, Bohr/Planck equations, and valence‑electron identification.