Rutherford, Planck and Bohr

Question 1

Rutherford

Answer 1

• postulated that the atom had a dense, positively charged nucleus that made up only a small fraction of the volume of the atom
• first to show atom being mostly empty space

Question 2

Planck

Answer 2

• developed the first quantum theory
• Energy emitted as electromagnetic radiation from matter comes in discrete bundles called quanta

Question 3

Planck Relation

Answer 3

• determines energy of a quantum
• E=hf
• h is Planck’s constant (60626 x 10^-34J•s)
• f is the frequency of the radiation (sometimes designated by the Greek letter nu, v)
  
  • frequency of emitted radiation is proprtional to the energy of that radiation

Question 4

Planck’s constant

Answer 4

• 6.626 x 10^-34J•s

Question 5

Bohr Model of the Atom

Answer 5

• A dense, positively charged nucleus is surrounded by electrons revolving aroung the nucleus in orbits with distinct energy levels
• Bohr placed restrictions on the possible values of angular momentum
• Bohr created an important conceptualization of atomic behavior but we now know electrons are NOT restricted to specific pathways but tend to be localized in certain regions of space
• proved inadequate to explain the structure and behavior of atoms containing more than 1 electron

Question 6

Bohr Formulas

Answer 6

• L=nh/2π
• E = - R_H/n²
• Angular momentum of an electron is directly proprtional to it’s Principle Quantum number
• The energy of the electron increases expontially with the Principle Quantum Number

Question 7

ground state

Answer 7

• atom at the state of lowest energy (smallest, lowest-energy radius)
• n=1

Question 8

excited state

Answer 8

• when at least 1 electron has moved to a subshell higher than normal energy

Question 9

Atomic Emission Spectra

Answer 9

• When electrons return from the excited state to the ground state, they emit an amount of energy that is exactly equal to the energy difference between the 2 levels
• sometimes the electromagnetic energy emitted corresponds to a frequency in the visible light range
• used as a fingerprint for the elements

**moves higher to lower

Question 10

AHED

Answer 10

• As electrons go from a lower energy level to a higher energy level, they get AHED
• Absorb Light
• Higher potential
• Excited
• Distant (from nucleus)

Question 11

Electro magnetic Energy Emission of Photons equation

Answer 11

• E=hc/λ
  
  • h = Plancks constant (6.626 x 10^-34J•s)
  • c = speed of light (3.00 x 10⁸ m/s)
  • λ = wave length of the radiation
  • combination of E=hf and c=fλ

Question 12

Name the 3 series of hydrogen emission spectrum

Answer 12

1. Lyman Series
   
   • group of H emission lines transitioning from n ≥ 2 to n = 1
   • larger energy transitions; therefore has shorter photon wavelengths
   • UV light
2. Balmer Series
   
   • transitions from energy levels n ≥ 3 to n = 2
   • visable light
3. Paschen series
   
   • transitions from n ≥ 4 to n = 3
   • infared

Question 13

Equation for energy associated with a change in the principal quantum number

Answer 13

E = hc/λ = -R_H [1/n²_i - 1/n²_f]

• R_H = Rydberg Unit of energy = 2.18 x 10^-18 J/electron
• energy of the emitted photon corresponds to the difference in energy between the higher-energy initial state and the lower-energy final state
• wavelength of emitted proton is inversely proportional to the energy of that photon
• the energy emitted or absorbed by an atom will increase as the energy level of the excited electron increases (decreases as energy level decreases)

Question 14

Atomic Absorption Spectra

Answer 14

• The atomic absorption spectra of an element is unique
• for an electron to jump from a lower energy level to a higher one, it must absorb an amount of energy equal to the energy difference of the 2 levels
• These wavelengths correspond to the wavelengths of emission
• Identification of elements in the gas phase requires absorption spectra

**moves lower to higher