Quantum mechanics

Question 1

Define spectroscopy:

Answer 1

Study of the relationship between matter and electromagnetic interaction

Question 2

Relationship between frequency and wavelength? Energy and frequency?

Answer 2

1. Inversely proportional
2. Proportional

Question 3

From lowest energy to highest energy, segment the electromagnetic spectrum:

Answer 3

1. Radio waves
2. Microwave radiation
3. Infrared radiation
4. Visible light
5. Ultraviolet radiation
6. X-rays
7. Gamma rays

Question 4

As energy levels increase, the space between levels:

Answer 4

gets smaller, i.e. converges

Question 5

Briefly describe the hydrogen emission spectrum:

Answer 5

Electrons falling from energy levels higher than n = 1 emit UV radiation, from higher to n = 2 emit visible light, from higher to n = 3 emit infrared radiation.

Question 6

Energy level n = infinity means:

Answer 6

That the electron has been removed from attraction to the nucleus

Question 7

Explain the emission line spectrum:

Answer 7

If electrons absorb energy, they move up energy levels (unstable relative to ground state) and emit equivalent energy to move back down. Corresponds to the wavelength of visible light released, which in turn shows the emission line spectrum.

Question 8

Quantum number n represents:

Answer 8

The principal quantum number, i.e. the energy level

Question 9

Quantum number l represents:

Answer 9

The secondary quantum number; angular momentum quantum number; i.e. the subshell divisions of n

Question 10

Valid values of n?

Answer 10

1 -> infinity

Question 11

Valid values of l:

Answer 11

0 -> (n-1)

Question 12

Letter codes of l are? How many electrons in each?

Answer 12

1. s, p, d, f, g…
2. 2, 6, 10, 14, 18…

Question 13

Quantum number m(l) represents:

Answer 13

The magnetic quantum number, i.e. the individual orbitals within the subshells

Question 14

Valid values of m(l):

Answer 14

• l -> +l

Question 15

Quantum number m(s) represents:

Answer 15

The spin quantum number, i.e. the direction in which an electron in an orbital spins

Question 16

Valid values of m(s):

Answer 16

-1/2, 1/2

Question 17

State the Aufbau principle.

Answer 17

Electron orbitals are filled up from lowest energy level up, i.e. building up.

Question 18

State Hund’s rule.

Answer 18

In the case of degenerate orbitals (i.e. with the same energy level), each orbital is filled with a single electron before doubling up.

Question 19

State the Pauli exclusion principle.

Answer 19

No two electrons may have the same quantum numbers; therefore each orbital may only have two electrons spinning oppositely

Question 20

From left to right on the periodic table, with the lanthanides/actinides last, name the quantum “blocks” of the periodic table:

Answer 20

s -> d -> p -> f

Question 21

Name four exceptions to the Aufbau principle and why they are exceptions:

Answer 21

1. Copper
2. Chromium
3. Molybdenum
4. Silver

Copper and silver move a 4s electron to the 3d orbital for a complete 3d shell. Chromium and molybdenum movie a 4s electron to the 3d orbital for a half-full 3d shell.

Question 22

Why might an element be multivalent?

Answer 22

For the sake of stability - lose or gain electrons to become a noble gas, or get rid of s electrons (less stable)

Question 23

Shape of an s orbital?

Answer 23

Spherical

Question 24

Shape of a p orbital?

Answer 24

“peanut” shaped, along the x, y, and z axes respectively

Question 25

What is the absorption spectrum? How does it compare to the emission spectrum?

Answer 25

The absorption spectrum is the energy absorbed by the electron when it gains energy. It will overlap perfectly with the emission spectrum.