u3: development of model of atom Flashcards
dalton’s 4 conclusions (1809)
- all matter is made of atoms that can’t be created, destroyed, or broken into smaller particles
- atoms of one element can’t be changed into atoms of another element
- atoms from one element have the same properties, atoms from different elements have different properties
- atoms of elements combine in specific proportions to form compounds
cathode tube
- sealed glass tube w/ two electrodes
- electrodes connected to power source where charges move from cathode (+) to anode (-)
- used by J.J. Thomson to show tht cathode elctrode rays were attracted to positively charged plate
thomson’s 3 conclusions
- atoms have small particles called electrons that have a small mass
- electrons embedded in a sphere of positive charge to maintain atom neutrality
- discovery of electrons proved that atoms is further divided into smaller particles
wht did rutherford determine based on his gold foil experiment (1911)
+wht couldnt he explain
- atom consists of electrons rapidly moving around positively-charged dense nucleus containing protons
- atoms has mostly empty space
- could not explain movement/position of electrons in atom
issues with rutherford’s planetary model
- accelerating charges create light (EMR) so electron should emit light while orbiting nucleus
- it should also lose energy and collapse into nucleus
- but, atoms are stable
what did max planck conclude
- energy is not continuous
- energy of oscillating atoms in heated solid were multiples of small quantities of energy
how are wavelength and energy related
- short wavelength: high energy
- long wavelength: low energy
how does temperature impact radiation
increase in temp shifts the wavelength to become visible
quantum
- small, discrete, indivisible quantity
- called photons for light/EMR
wha did einstein contribute
- light emitted by a hot solid is quantized and comes as bursts, not continuously
- suggested classical physics was wrong
what kind of light causes electron to eject
- classical physics says light w/ intensity
- it’s acc the frequency (colour) of light
photoelectric effect
ejection of an electron only results when a minimum quantity of energy from a photon is transferred to the electron
photon
- small packet of light energy of a specififc frequency
- E=hv = hf where h is plank’s constant and v is the frequency
plancks constant
6.626 x 10^-34 J(s)
what do blackbody radiation and photoelectric effect show
that energy is quantized
how did Bohr refine rutherford’s model?
- accounted for stability that energy is quantized
- electrons orbit nucleus in defined energy states with set angular values (function of integer n and h: plank’s constant)
- as such, electrons cannot collapse into nucleus
what did Bohr base his model off of
line spectra of hydrogen
electrons in their ground state..
don’t give off energy
what is line spectra
it is a visual rep for the quantum of energy released when electrons fall back to ground state
why can electron only have certain allowable energies?
bc. if light absorbed/released from atom is quantized, energy of atom must also be quantized
when do electrons jump from ground state to excited state?
if electrons absorb a specific amount of energy (quantum)
what happens when electrons fall back to ground state?
quantum of energy is released in the form of light (line spectra)
what couldn’t bohr’s model explain?
line spectra for atoms besides hydrogen
relationship between wavelength and frequency
as wavelength increases, frequency decreases
