Matter

Question 1

What is the Rydberg formula?

Answer 1

1/λ = R*((1/m^2) - (1/n^2))

Question 2

What are the names for the values when m = 1, 2 and 3, and what are their corresponding radiations?

Answer 2

m=1: Lyman series (UV)
m=2: Balmer (visible + UV)
m=3: Paschen (IR)

Question 3

What did Bohr state?

Answer 3

That only a discrete set of possible states with energies En is allowed.

Question 4

What equation did Bohr come up with to prove this? How can we use this equation with the Rydberg formula?

Answer 4

1/λ = Ei/hc - Ef/hc

Compare this with Rydberg formula to come up with values for Ei and Ef, where i and f and initial and final energies.

Question 5

What is the equation for the Bohr radius, a0?

Answer 5

a0 = (ϵ0h^2)/(pime*e^2)

Question 6

How do you find the radius of an electrons orbit in an atom (rn)?

Answer 6

a0 * n^2

Question 7

What is the equation for the velocity of an electron oriting a nucleus?

Answer 7

vn = h/(2pimena0) = e^2/(2nϵ0*h)

Question 8

What is the equation for the potential energy of anorbiting electron?

Answer 8

e^2/(4piϵ0rn)

Question 9

How do you work out the energy of an electron?

Answer 9

KE + PE = 1/2mevn^2 - e^2/(4piϵ0rn). Substitute in vn and rn and rearrange

Question 10

What do you get when you compare the energy of an electron with the Rydberg formula?

Answer 10

E = hc/λ = hcR((1/m^2)-(1/n^2))

Question 11

What is the equation for the Rydberg constant?

Answer 11

R = (mee^4)/(8ϵ0^2h^3c)

Question 12

How does the energy of an electron change when n increases?

Answer 12

E becomes less and less negative.

Question 13

What is ħ?

Answer 13

ħ = h/2pi

Question 14

What is the equation for λ, the de Broglie wavelength?

Answer 14

λ = h/p, p = h/λ = ħk

Question 15

What is the equation for the de Broglie wavelength in terms of r? What does this mean?

Answer 15

nλ = 2pi*r

This means there is an integer umber of λ’s around circumference of orbit - standing waves are formed.

Question 16

How were electrons proved to act like particles and waves?

Answer 16

The electrons were reflected (wave) and diffracted (particle). Reflected by emitting electron beam at nickel crystal and detecting the reflected beam. Diffracted by emitting beam through aluminium foil and observing diffraction pattern.

Question 17

What is the equation for Braggs Law?

Answer 17

nλ = 2d*sin(theta)

Question 18

Why do electrons diffract through aluminium foil?

Answer 18

The spaces between the atoms act as a slit, and the electrons diffract between the atoms.

Question 19

How do you use the de Broglie wavelength equation for real things such as grains of sand and neutrons?

Answer 19

Get given the things mass and velocity or something, and use the equations to work out the wavelength.

Question 20

Why does diffraction sometimes not occur? How can you solve this?

Answer 20

If the particle is moving too fast and therefore its wavelength is too small. Can be solved by slowing the particle down.