05/17/25

Question 1

What is the atomic number (Z)?

Answer 1

The number of protons in an atom.

Question 2

What is the mass number (A)?

Answer 2

The sum of protons and neutrons in an atom.

Question 3

What is an isotope?

Answer 3

Atoms of the same element with different mass numbers (different neutrons).

Question 4

What are cations and anions?

Answer 4

Cations lose electrons (+), anions gain electrons (−).

Question 5

Describe Rutherford’s atomic model.

Answer 5

Atom has a small, dense nucleus with electrons orbiting around.

Question 6

What is the Bohr model?

Answer 6

Electrons exist in quantized orbits with specific energy levels.

Question 7

What is the quantum mechanical model?

Answer 7

Electrons exist in orbitals as probability clouds.

Question 8

Define principal quantum number (n).

Answer 8

Indicates energy level and distance from nucleus.

Question 9

Define azimuthal quantum number (l).

Answer 9

Indicates orbital shape: s=0, p=1, d=2, f=3.

Question 10

Define magnetic quantum number (m_l).

Answer 10

Specifies orbital orientation in space (−l to +l).

Question 11

Define spin quantum number (m_s).

Answer 11

Specifies electron spin direction: +½ or −½.

Question 12

What causes paramagnetism?

Answer 12

Unpaired electrons that are attracted to magnetic fields.

Question 13

What causes diamagnetism?

Answer 13

Paired electrons that are weakly repelled by magnetic fields.

Question 14

What causes ferromagnetism?

Answer 14

Aligned unpaired electron spins in domains (e.g., Fe, Co).

Question 15

What is the Aufbau Principle?

Answer 15

Electrons fill lower energy orbitals first.

Question 16

What is Hund’s Rule?

Answer 16

Electrons fill degenerate orbitals singly before pairing.

Question 17

What is the Pauli Exclusion Principle?

Answer 17

No two electrons in an atom can have the same four quantum numbers.

Question 18

What is effective nuclear charge (Z_eff)?

Answer 18

Net positive charge felt by outer electrons, Z_eff ≈ Z - shielding.

Question 19

How do atomic trends vary across the periodic table?

Answer 19

↑Ionization energy, ↑Electron affinity, ↑Electronegativity, ↓Atomic radius across a period.

Question 20

Why are s-orbitals lower in energy?

Answer 20

They penetrate closer to the nucleus and experience less shielding.

Question 21

What is ionization energy?

Answer 21

Energy required to remove an electron from a neutral atom.

Question 22

What is electron affinity?

Answer 22

Energy released when an atom gains an electron.

Question 23

What is electronegativity?

Answer 23

Atom’s tendency to attract electrons in a bond.

Question 24

What is the photoelectric equation?

Answer 24

KE = hf − ϕ (ϕ = work function).

Question 25

What is the equation for photon energy?

Answer 25

E = hf or E = hc/λ.

Question 26

What are HOMO and LUMO?

Answer 26

Highest occupied and lowest unoccupied molecular orbitals.

Question 27

How does conjugation affect fluorescence?

Answer 27

More conjugation lowers HOMO-LUMO gap → visible emission.

Question 28

What is second ionization energy?

Answer 28

Energy needed to remove a second electron, always greater than the first.

Question 29

What is PES?

Answer 29

Photoelectron spectroscopy: shows binding energies and quantities of electrons.

Question 30

What is mass defect?

Answer 30

Mass difference converted to binding energy when nucleus forms (ΔE = Δm·c²).

Question 31

What are the types of nuclear decay?

Answer 31

Alpha, beta-minus, beta-plus, gamma, electron capture.

Question 32

What is alpha decay?

Answer 32

Emission of a helium nucleus (⁴₂He), A−4, Z−2.

Question 33

What is beta-minus decay?

Answer 33

Neutron → proton + electron; Z increases by 1.

Question 34

What is beta-plus decay?

Answer 34

Proton → neutron + positron; Z decreases by 1.

Question 35

What is gamma decay?

Answer 35

Photon emission from excited nucleus; no change in A or Z.

Question 36

What is electron capture?

Answer 36

Proton captures electron → converts to neutron; Z decreases by 1.

Question 37

How does mass spectrometry work?

Answer 37

Separates ions by mass-to-charge ratio (m/z).

Question 38

What is the difference between Bohr and quantum models?

Answer 38

Bohr uses orbits, quantum uses probability-based orbitals.

Question 39

What are some MCAT traps?

Answer 39

Incorrect electron removal (4s vs 3d), mixing EA with IE, trend misapplication.