SECTION 1 - QUANTUM MECHANICAL MODEL OF ATOM Flashcards
Quantum mechanics
Model that describes how electrons exist in atoms and helps explain chemical and physical properties of the elements
Parts of an atom:
- Proton (p)
- Neutron (n)
- Electron (e-)
Electromagnetic radiation
Tool to understand electronic structure in atom and consists of a wave of energy
Frequency
Number of cycles per second (s-1) (v)
Wavelength
Distance the waves travels during one cycle (nm, m , um) (lamda)
Amplitude
Height of crest of each wave
Relationship between frequency and wavelength
Inversely proportional. Greater frequency = small wavelength, small frequency = big wavelength)
What type of ER has the longest wavelength (smallest frequency)
Radio
What type of visible light has the shortest frequency
Red
What type of ER has the shortest wavelength (biggest frequency)
Gamma ray (produced by sun, stars, etc)
Speed of light
2.998 x 10^8 ms-1
Relationship between visible light and brightness/color
Amplitude determines the brightness and frequency/wavelength determines color
Interference
Phenomenon in which 2 waves combine by adding or subtracting waves
In phase (constructive interference)
Waves are in line and combine together = higher amplitude, higher intensity (bright)
Out phase (destructive interference)
Waves are not in line and subtract one another = no amplitude, no intensity (dark)
Wave-particle duality of light
Waves can exhibit particle like properties and particles can exhibit wave-like properties (photons)
Photoelectric effect
Albert Einstein demonstrated that light has properties of a particle. The experiment consisted of the emission of electrons when electromagnetic radiation hits a metal
2 reasons why light is not proven as a wave (photoelectric effect) (2)
- Light had to be a certain minimum frequency or no electron was ejected (if light was a wave, any frequency of light would work)
- There was no lag time and the current flowed as soon as light was hit at the metal (if light was a wave, dim light would have taken a while to have enough energy to kick out the electron)
Photon
Term by Einstein of a particle of light and viewing it as a “packet” of electromagnetic radiation and has characteristics of Plank’s constant
Planck’s constant
6.626 x 10^-34
Blackbody radiation
Conducted by Max Planck. Blackbody is an idealized object that absorbs all electromagnetic radiation it comes into contact with. It then emits thermal radiation in continuous spectrum according to temperature. Planck theorized that energy emitted by hot object is in the form of packets (photon)
Ephoton formula
h = c/lamda
What is the energy of a packet dependant on
Dependant on frequency of light. Photon of the right frequency hits an electron on the surface and supplies the right amount of kinetic energy to kick electron
Kinetic energy formula
KE = energy of photon - binding energy
Atomic spectra
The spectrum of the electromagnetic radiation emitted or absorbed by an electron during transitions between different energy levels within an atom. Viewable via prism
Niels Bohr
Developed a model for the atom to explain the atomic line spectra for the H atom
What did Bohr popstulate (3)
- Electrons can move in a circular orbit (wrong)
- Electrons have a fixed set of allowed orbits (energy states) at fixed distances from nucleus with principle quantum number n (correct)
- Electrons can jump from one allowed orbit to another with a certain energy
Energy of electron in an orbit formula
En = -2.179 x 10^-18J (z^2/n^2)
Excitation
Electrons absorbs energy and gains enough energy to move to a higher orbit
Relaxation
Electron releases energy (emitted) to go to a lower orbit
Ground state
Lowest energy level (n=1)