Unit 1: Quantum Mechanics

Question 1

What does quantum mechanics describe?

Answer 1

The physics of particles smaller than atoms, like electrons, protons, and neutrons.

Question 2

What is the main tool used to measure electrons?

Answer 2

Electromagnetic radiation (ER).

Question 3

What are the three characteristics of a wave?

Answer 3

Frequency (ν), wavelength (λ), and amplitude.

Question 4

What is the speed of light?

Answer 4

2.998 × 10^8 m/s.

Question 5

What is the relationship between speed of light, wavelength, and frequency?

Answer 5

c = λ × ν.

Question 6

What type of EM radiation has the longest wavelength?

Answer 6

Radio waves.

Question 7

What type of EM radiation has the shortest wavelength?

Answer 7

Gamma rays.

Question 8

What color of visible light has the longest wavelength?

Answer 8

Red.

Question 9

What color of visible light has the shortest wavelength?

Answer 9

Violet.

Question 10

What is constructive interference?

Answer 10

When waves are in phase and add to produce a larger amplitude.

Question 11

What is destructive interference?

Answer 11

When waves are out of phase and cancel each other out.

Question 12

What is the photoelectric effect?

Answer 12

Ejection of electrons from a metal surface when struck by light of sufficient frequency.

Question 13

What is a photon?

Answer 13

A packet (quantum) of light energy.

Question 14

What is Planck’s equation?

Answer 14

E = hν, where h = 6.626 × 10^-34 J·s.

Question 15

What is the threshold frequency (ν₀)?

Answer 15

The minimum frequency needed to eject electrons from a metal.

Question 16

What is the equation for kinetic energy in the photoelectric effect?

Answer 16

KE = E_photon - φ (work function).

Question 17

What is an atomic line spectrum?

Answer 17

Discrete wavelengths emitted by excited atoms returning to lower energy states.

Question 18

What did Bohr propose about electrons?

Answer 18

Electrons orbit the nucleus in quantized energy levels.

Question 19

What happens when an electron absorbs energy?

Answer 19

It moves to a higher energy level (excitation).

Question 20

What happens when an electron emits energy?

Answer 20

It drops to a lower energy level and emits a photon.

Question 21

What is the ground state?

Answer 21

The lowest energy level (n=1) of an atom.

Question 22

What equation determines energy levels of hydrogen?

Answer 22

E = -2.179 × 10^-18 J × (1/n²).

Question 23

What is wave-particle duality?

Answer 23

Light and small particles like electrons exhibit both wave and particle properties.

Question 24

What is the de Broglie equation?

Answer 24

λ = h / (mv), describing wavelength of a particle.

Question 25

What does the Heisenberg uncertainty principle state?

Answer 25

The position and momentum of a particle cannot be simultaneously known with precision.

Question 26

What happens to uncertainty in position as uncertainty in velocity decreases?

Answer 26

It increases, and vice versa.

Question 27

What are the four quantum numbers?

Answer 27

n (principal), l (angular), m_l (magnetic), m_s (spin).

Question 28

What does the principal quantum number (n) indicate?

Answer 28

Energy level and size of orbital.

Question 29

What does the angular momentum quantum number (l) describe?

Answer 29

Orbital shape (s, p, d, f).

Question 30

What does the magnetic quantum number (m_l) describe?

Answer 30

Orbital orientation in space.

Question 31

What are possible values for spin quantum number (m_s)?

Answer 31

+1/2 or -1/2.

Question 32

What is a node in an orbital?

Answer 32

A region of zero electron probability.

Question 33

What is Hund’s Rule?

Answer 33

Electrons fill degenerate orbitals singly before pairing.

Question 34

What is the Pauli Exclusion Principle?

Answer 34

No two electrons can have the same set of four quantum numbers.

Question 35

What is the Aufbau Principle?

Answer 35

Electrons occupy orbitals in order of increasing energy.

Question 36

What is effective nuclear charge (Z_eff)?

Answer 36

The net positive charge experienced by an electron.

Question 37

What is a diamagnetic atom?

Answer 37

An atom with all paired electrons and no magnetic properties.

Question 38

What is a paramagnetic atom?

Answer 38

An atom with unpaired electrons that exhibits magnetic properties.