u3: development of model of atom

Question 1

dalton’s 4 conclusions (1809)

Answer 1

• 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

Question 2

cathode tube

Answer 2

• 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

Question 3

thomson’s 3 conclusions

Answer 3

• 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

Question 4

wht did rutherford determine based on his gold foil experiment (1911)
+wht couldnt he explain

Answer 4

• 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

Question 5

issues with rutherford’s planetary model

Answer 5

• 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

Question 6

what did max planck conclude

Answer 6

• energy is not continuous
• energy of oscillating atoms in heated solid were multiples of small quantities of energy

Question 7

how are wavelength and energy related

Answer 7

• short wavelength: high energy
• long wavelength: low energy

Question 8

how does temperature impact radiation

Answer 8

increase in temp shifts the wavelngth to become visible

Question 9

quantum

Answer 9

• small, discrete, indivisible quantity
• called photons for light/EMR

Question 10

wha did einstein contribute

Answer 10

• light emitted by a hot solid is quantized and comes as bursts, not continuously
• suggested classical physics was wrong

Question 11

what kind of light causes electron to eject

Answer 11

• classical physics says light w/ intensity
• it’s acc the frequency (colour) of light

Question 12

photolectric effect

Answer 12

ejection of an electron only results when a minimum quantity of energy from a photon is transferred to the electron

Question 13

photon

Answer 13

• small packet of light energy of a specififc frequency
• E=hv = hf where h is plank’s constant and v is the frequency

Question 14

plancks constant

Answer 14

6.626 x 10^-34 J(s)

Question 15

what do blackbody radiation and photoelectric effect show

Answer 15

that energy is quantized

Question 16

how did Bohr refine rutherford’s model?

Answer 16

• 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

Question 17

what did Bohr base his model off of

Answer 17

line spectra of hydrogen

Question 18

electrons in their ground state..

Answer 18

don’t give off energy

Question 19

what is line spectra

Answer 19

it is a visual rep for the quantum of energy released when electrons fall back to ground state

Question 20

why can electron only have certain allowable energies?

Answer 20

bc. if light absorbed/released from atom is quantized, energy of atom must also be quantized

Question 21

when do electrons jump from ground state to excited state?

Answer 21

if electrons absorb a specific amount of energy (quantum)

Question 22

what happens when electrons fall back to ground state?

Answer 22

quantum of energy is released in the form of light (line spectra)

Question 23

what couldn’t bohr’s model explain?

Answer 23

line spectra for atoms besides hydrogen