MODULE 8 IQ 3

Question 1

limitations of rutherford’s atomic model

Answer 1

• could not explain electron/atomic stability
• no restriction on orbit of electrons –> produce continuous spectra –> contradicts existing discrete emission lines of hydrogen atoms

Question 2

bohr’s 1st postulate

Answer 2

electrons orbit in stationary states and do not radiate energy –> stays in quantised energy levels

Question 3

bohr’s 2nd postulate

Answer 3

transition between stationary states would be accompanied by absorption or emission of energy in the form of EMR

Question 4

bohr’s 3rd postulate

Answer 4

angular momentum is quantised
- electrons undergo uniform circular motion due to electrostatic attraction between itself and nucleus

Question 5

limitations of bohr’s atomic model

Answer 5

• did not clearly explain discrete emission of photons beyond hydrogen
• didn’t explain why hydrogen spectral lines were not of equal intensity
• zeeman effect –> when gas is excited in magnetic field, emission spectrum shows a splitting of spectral line

Question 6

balmer equation

Answer 6

calculate wavelengths of these lines
1/wavelength = R(1/m^2 - 1/n^2)

Question 7

rydberg’s equation

Answer 7

predict wavelength of proton absorbed or emitted when an electron transitions between orbits of different states

Question 8

louis de broglie equation

Answer 8

wavelength = h/mv

Question 9

louis de broglie model

Answer 9

linked waves and particles together
- any moving particle has an associated wavelength
- should be possible to detect wave nature of electrons if they were diffracted from surface of crystal

Question 10

using de broglie to explain stationary states

Answer 10

applying particle-wave duality –> electron orbits were standing waves (radius of each energy level was an integer multiple of electron’s wavelength)
n x h/2(pi) = 2(pi)r
- now orbit in standing waves, they do not lose energy

Question 11

davisson and gemer

Answer 11

tried to observe the scattering of electrons onto the surface of a piece of nickel
- accidentally annealed the metal, producing a smooth region of large crystals
- formed interference pattern –> calculate wavelength of electron by using diffraction methods: wavelength = 2dsin(theta)

Question 12

erwin schrodinger model of the atom

Answer 12

• defined a wave function through solving a differential equation derived from the forces acting upon an electron
• square of this wave gave probability that an electron would be at that distance from the nucleus