Electronic Structure And Periodicity Flashcards
Electromagnetic spectrum
-Includes all forms of electromagnetic radiation (radiant energy)
~gamma rays, X rays, Ultraviolet, Visible light (ROYGBIV), Infrared, microwaves, radio waves
-characterized by frequency, wavelength, and amplitude
Gamma rays
-shortest wavelength
(10^-12 m)
-highest frequency
(10^20 Hz)
X rays
- wavelength = 10^-10 m
- frequency = 10^18 Hz
Ultraviolet
- wavelength = 10^-8 m
- frequency = 10^16 Hz
Visible light
Wavelengths: -Violet = 380nm (3.8x10^-7 m) -Indigo = 420nm -blue = 490nm -green = 520nm -yellow = 600nm -orange = 690nm -Red = 780nm (7.8x10^-7 m) Frequency = ~10^15 Hz (depending on color)
Infrared
- wavelength = 10^-6 m
- frequency = 10^14 Hz
Microwaves
- wavelength = 10^-3 m
- frequency = 10^10 Hz
Radio waves
- wavelength = 1 m
- frequency = 10^8 Hz
Frequency
- (v)
- the # of wave peaks that pass a given point, per unit time
- 1/s
Wavelength
- (lambda)
- the distance from 1 wave peak to the next
- m
Amplitude
- (A)
- the height of the wave (from center line to peak)
Frequency and wavelength relationship
- inversely related
- longer wavelength = lower frequency
- shorter wavelength = higher frequency
- Wavelength x Frequency = speed
- wavelength = speed/frequency
- frequency = speed/wavelength
- speed = the speed of light (2.998x10^8) unless otherwise specified
Diffraction and interference
- diffraction is the bedding of light around an object
- interference occurs when 2 or more waves superpose to form a new wave
- constructive = larger wave
- destructive = smaller or no wave
Photoelectric effect
-irritating a clean metal surface with light causes electrons to be ejected from the metal
Planck’s postulate
- a beam of light behaves as if it were a stream of small particles (photons)
- the energy of the photons is related to their frequency and wavelength
E = hv or E = hc/y
-h= Planck’s constant (6.626x10^-34)
-v = frequency
-c = speed of light (2.998x10^8)
-y = wavelength
-often asks for answer in per-mol basis, not per-photon (as answer gives), multiply per-photon energy by Avagadro’s number (6.02x10^23) to find per-mol energy
- higher frequency & shorter wavelength = higher E
- lower frequency & longer wavelength = lower E
Intensity & frequency
- energy of a photon depends on its wavelength and frequency (not intensity)
- intensity of a light beam is a measure of the number of photons in the beam
- frequency is a measure of the energy of the photons
Work function
- the amount of energy necessary to eject an electron from a metal
- depends on the metal (specific to each)
- lowest for group 1A & 2A elements
Atomic line spectra
- atoms give off light when energetically excited
- light is not continuous and only occurs at certain wavelength
- different atoms produce distinct spectra that are unique to that element
Bohr model
- proposed that electrons move in circular orbits around the nucleus
- each orbit has its own radius which is directly related to energy (n)
- as radius increases, energy increases(E-final)-(E-initial) = hv
- when an electron falls to a lower energy it releases a photon
- when an electron jumps to a higher energy, it has absorbed energy
*an electron cannot reside between orbits
Balmer-Rydberg equation
E = R [(1/m^2) - (1/n^2)]
- E = energy (J)
- R = 2.178x10^-18
- m = final energy level
- n= initial energy level
*can find wavelength or frequency using the energy
De Broglie equation
- perhaps matter is wavelike, as well as particle-like
- double-slit experiment
(Y) = h/mv
- y = wavelength
- h = planck’s constant (6.626x10^-34)
- m = mass
- v = velocity
quantum mechanical model of an atom
- Erwin Shrodinger
- it is impossible to know precisely where an electron is and what path it follows
- the very act of determining an electrons position (requires input of energy) causes the position to change
Wave function
- orbital
- found by solving a wave equation
- characterized by 4 parameters (quantum numbers)
- n
- l
- m(l)
- m(s)
(n)
Principal quantum number
- a positive integer
- relates directly to size and energy of orbital
- for atoms with more than 1 electron, the energy level of an orbital depends on both “n” and “l”
- as n increases, the number of allowed orbitals increases and those orbitals become larger (allows an electron to be further from the nucleus)
- the energy of an electron in the orbital increases as quantum number n increases