Topic 4-Quantum Theory

Question 1

What are EMR waves made of?

Answer 1

EMR is made up of propagating electric and magnetic fields.

Question 2

What is frequency? What is the symbol for it?

Answer 2

Frequency is the number of cycles a wave undergoes per second. The symbol is a “nu”

Question 3

What is a wave’s wavelength?

Answer 3

Wavelength is the distance of one cycle of a wave.

Question 4

What is the relationship between the wavelength and frequency?

Answer 4

Wavelength and frequency have an inverse relationship.

Question 5

What is a wave’s amplitude?

Answer 5

An amplitude is the height of the crest in a wave. It also refers to the intensity/brightness.

Question 6

What is constructive interference?

Answer 6

When two waves are in phase and come together to create a bigger amplitude (bright spots)

Question 7

What is destructive interference?

Answer 7

When two waves are out of phase, they cancel each other (dark spots).

Question 8

What are the 3 proofs of the particle model of light?

Answer 8

1. Black body radiation
2. Photoelectric effect
3. Atomic Spectra

Question 9

What is the photon theory?

Answer 9

EMR can be viewed as a stream of particles called photons.

Question 10

How do I calculate the energy of one photon? (2 ways)

Answer 10

Take the frequency of the photon and multiply it by Plank’s Constant.

Take the speed of the photon, multiply it by Plank’s Constant, and divided it by its wavelength.

Question 11

What is the:

Lyman Series and Balmer Series for the hydrogen atomic spectra?

Answer 11

The Lyman Series describes the UV series and the Balmer Series describes the visible series of the HYDROGEN atomic spectra.

Question 12

What is the first principle of the Bohr’s Atomic Model of the Hydrogen Atom?

Answer 12

1. The energy level in an atom must be quantized (must be on an energy level, not in between) and each level associates with a fixed circular orbit.

Question 13

What is the second principle of the Bohr’s Atomic Model of the Hydrogen Atom?

Answer 13

When changing from a higher energy quantized level to a lower energy quantized level, photon emits energy. Vice verse, the photon absorbs energy

Question 14

When is the energy of an electron equal to 0?

Answer 14

When the electron has a quantum number equal to infinity.

Question 15

When is the energy of an electron the lowest (most negative)?

Answer 15

When the electron has a quantum number equal to 1.

Question 16

which quantum numbers have the largest energy difference?

Answer 16

Between n=1 and n=2.

Question 17

What are some limitations of the Bohr Model?

Answer 17

1. It can only apply to one-electron species.
2. Electrons moving in orbit will lose energy which means the electron will ultimately be attracted to the nucleus and collapse the atom.

Question 18

What did de Broglie propose in 1924?

Answer 18

de Broglie proposed that if light can be thought as moving particles, moving particles can be thought of as waves.

Question 19

When is the wave property of objects significant?

Answer 19

All matter possess wave properties. However, it is only when the mass is small that the wave property is significant.

Question 20

What is the Heisenberg Uncertainty Principle

Answer 20

It is impossible to know the exact position and momentum of a particle simultaneously.

Question 21

Why does Bohr’s Model violate Heisenberg’s Uncertainty Principle?

Answer 21

In Bohr’s Model, it assigned fixed orbits (position is known) and it had fixed energies (momentum is known).

Question 22

What are 3 properties of a standing wave?

Answer 22

1. The waves must oscillate between two fixed limits.
2. Some points along the string do not move (nodes)
3. Once the limits are fixed, the wavelengths are quantized. That is, only certain while number of half-wavelengths is allowed

Question 23

What is a wave function?

Answer 23

A wave function describes the motion of an electron in terms of the time and position corresponding to its quantum number.

Question 24

What does the n stand for?

Answer 24

The principal quantum number.

Question 25

What does l stand for? What does it refer to?

Answer 25

l is the angular momentum quantum number. It refers to the shape and type of orbital

Question 26

What does ml stand for? What does it refer to?

Answer 26

ml is the magnetic quantum number. It refers to the orientation of the orbital in space around the nucleus.

Question 27

What are degenerate orbitals?

Answer 27

Subshells that have the same energy.

Question 28

What does a squared wave function represent?

Answer 28

A squared wave function represets the probabiity of finding an electron at a particular point within an atom.

Question 29

In the atom, where is the highest density of electrons?

Answer 29

The highest density of electrons is greatest near the nucleus of the atom.

Question 30

Where in the p orbital will you find zero electrons?

Answer 30

The nodal plane.