Bohr Model

What were 3 observations that involved matter and light that created problems for physicists in the early 20th century? 

Blackbody radiation

Photoelectric effect

Atomic spectra

Name the 3 temperatures and the color a solid object becomes for each. 

Red-1000 K

Orange-1500 K

White- 2000K

What are characteristics of a heated object and the emitted light a characteristic of? 

blackbody radiation

True or false. Classical electromagnetic theory can explain blackbody radiation observations. 

false

What happens when monochromatic light of sufficient frequency shines on a metal plate? 

a current flows

What do the confusing features of the current represent? 

a presence of a threshold frequency

an absence of a lag time

True or false. The wave model does not explain the Photoelectric effect

True

Compare the difference to light from electrically excited gaseous atoms to sunlight when it passes through a slit and is refracted by a prism. 

Electrically excited gaseous atoms create a line spectrum (series of fine lines and specific frequencies separated by black spaces)

Sunlight create a continuous spectrum (rainbow)

What does each spectrum of the atomic spectra represent? 

a characteristic of the atom producing it

What kind of energy level can the H atom have? 

stationary states

What is each energy level of an H atom associated with? 

a fixed circular orbit of electron around the nucleus

What does it mean to be in a stationary state? 

the atom does not radiate any energy

What are the only ways for an atom to change to another stationary state? 

absorbing or emitting a photon

Who was Niels Bohr a student of?

Rutherford (gold-foil experiment discovering the atom had a nucleus)

What did Niels Bohr study?

the H atom

What did Niel Bohr seek to understand?

the electrons in the atom

What model did Bohr come up with for the H atom? 

planetary model, where electrons orbit the nucleus in circular pathways

What specificity did Bohr have in his model? 

only certain orbits are allowed and electrons orbit at specific distances from the nucleus

What can the electrons in the H atom occupy? 

a specific orbit

Explain the relationship between an electron's potential energy and its distance from the nucleus. 

direct relationship to each other (i.e. as distance of an electron to the nucleus increase, the electron’s energy potential energy increases)

How do electrons get from one orbit to another? What does this mean?

by jumping fully, meaning electrons can never be found in between

According to Bohr's Model of the atom, how do electrons travel? 

in orbits around the nucleus

What distances do the orbits take? 

fixed distances

How many electrons can fill the first orbit? 

two electrons (limited volume)

How many electrons can fill the second orbit? 

eight electrons (more volume available the further the orbital)

What does the quantum number represent? 

n, a positive energy, that shows the size (radius) of an electron orbit

What does it mean for an electron to be in a ground state? 

when n=1, it is the electron’s lowest energy level

What does it mean for an electron to be in an excited state? 

when n>1, the electron is in a higher energy state further from the nucleus

Define how absorption works

if an H atom absorbs a photon, it moves up an anergy level

Explain how emission works

when an H atom produces and releases a photon, it moves down an energy level

What does the Bohr model account for? What causes the lines to arise? 

line spectra, lines arise due to energy level differences

When does visible series of spectral lines occur? 

when electrons drop to n=2 (first excited state)

When do infrared lines occur? 

when electrons drop to n=3

When do ultraviolet lines occur? 

when electrons drop to n=1

Explain why the atomic spectrum is not continuous. 

because atomic spectrum’s energy is not continuous, meaning only certain states are allowed

What does the Bohr model fail to predict? What is the reason? 

spectra of other atoms because it only works with one-electron models

What two things does Bohr model not account for? 

electron-electron repulsion and electron-nucleus attractions

True or false. Electrons move in fixed, defined orbits. 

False