Chapter 2 - The Quantum Mechanical Model of the Atom Flashcards
How do electrons behave?
much differently than large objects (classical physics does not describe electrons)
What is Quantum Mechanics?
physics of the really small, forms the basis of our understanding of mater and its behaviour at the subatomic level
What is light?
A form of electromagnetic radiation
Composed of perpendicular oscillating waves, one for the electric field and one for the magnetic field
In what way does light move?
At a constant speed. notified by ‘c’ (speed of light) = 3.00x10^8 m/s
What is Amplitude?
vertical height of a crest or depth of a trough
determines the lights intensity/ brightness
greater amplitude = greater intensity
What is Wavelength?
distance between 2 adjacent crests or troughs etc. is measured in units like metres, micrometres and nanometres
What is frequency?
the number of waves that pass a point in a given period of time
units are cycles per second (s^-1) or hertz (Hz)
1s^-1 = 1Hz
What is the relationship between wavelength and frequency?
they are inversely proportional
What is the equation for Frequency?
Frequency (s^-1) = Speed of light (3.00x10^8) / wavelength (m)
What is total energy (light as a wave)?
proportional to the amplitude of the waves and their frequency
The larger the amplitude, the more force it has
The more frequently the waves strike, the more total force there is.
On the electromagnetic spectrum what does a shorter wavelength mean?
(high frequency) light has higher energy
Which wave of light has the lowest energy?
Radio-wave light
Which wave of light has the highest energy?
Gamma-ray light
What are some examples if high-energy electromagnetic radiation and what could they do to molecules?
UV, X-ray, Gamma can potentially damage biological molecules
What is the wavelength of Gamma rays?
10^-15 m
What is the wavelength of radio waves?
10^5 m
list the different types of wavelength from low to high energy
Radio, Microwave, Infrared, Visible , Ultraviolet, X-Ray, Gamma Ray
What is the region for visible light?
between 400nm - 750nm (small)
What is Interference (waves)?
the interaction between multiple waves
What is constructive interference?
waves that are in phase and add to make a larger wave
What is destructive interference?
waves that are out of phase and cancel each other out
What is diffraction?
When propagating waves encounter an opening in a barrier and bend around it. (travelling particles do not diffract)
What does the diffraction of waves through 2 slits result in?
an interference pattern (alternating regions of constructive and destructive interference) (waves out of phase = dark spot & vice versa)
What is the photoelectric effect?
that when light hits a metal surface, electrons can be ejected
What is the driving force in the photoelectric effect?
the frequency of the light. There is a threshold frequency needed to be met before electrons are emitted. High frequency light from a dim source causes electron emission without any lag time.
What is the equation for Photon Energy?
E = hv (h=Planck’s Constant) (v=frequency)
What is Planck’s Constant?
6.626 x 10^-34 (J/s)
What is the equation for Frequency?
v=c/λ(c=speed of light) (λ=wavelength)
What is the atomic spectra?
when atoms absorb energy, extra energy in atoms or molecules can be released as light (used in fireworks)
How do we see different colours?
different atoms (elements) have distinct wavelengths that they emit
What does a line spectra show?
the different wavelengths of light emitted. Easy comparison between elements
Why was the Bohr model of the atom needed?
the nuclear model of the atom does not explain what structural changes occur when the atom gains or loses energy
What was Bohr’s major idea about electrons in relation to the atom?
the energy of the atom was quantised, and that the amount of energy in the atom was related to the electron’s position in the atom.
What did De Broglie propose?
particles could have wave-like character
What is De Broglie’s relation?
wavelength = Planck’s constant / (mass x velocity) λ = h/mv
What is Heisenberg’s uncertainty principal?
Impossible to know precisely where an electron is and what path it follows
What is the wave/particle description of light?
by mathematical mode (can’t see atoms and observe behaviour directly)
What does Schrodinger’s equation calculate?
the probability of finding an electron with a particular amount of energy at a particular location in the atom
What do the solution of Schrodinger’s equation calculate?
a probability distribution map of a region where the electron is likely to be found called an orbital
What are the 4 Quantum numbers?
Principal quantum number
Angular momentum quantum number
Magnetic quantum number
Spin quantum number
What is the principal quantum number represent and what is it’s symbol?
Energy level, denoted by ‘n’
What does the angular momentum number represent and what is it’s symbol?
Orbital type, denoted by ‘l’
what does magnetic quantum number represent and what is it’s symbol?
position of an orbital in X-Y-Z plot. denoted by ‘m sub l’ (m with l as like a small lower letter)
What does spin quantum number represent and what is it’s symbol?
orientation of the spin of the electron, denoted by ‘m sub s’ (m with s as like a small lower letter)
What is the number range for Principal Quantum number?
whole number integer ≥ 1
In principal quantum number as n increases what happens to the energy of electron and the distance from nucleus?
they both increase
In the angular momentum quantum number what values can l have?
integer values from 0 to (n-1)
If the l value is 0 what is the letter designation?
s
If the l value is 1 what is the letter designation?
p
If the l value is 2 what is the letter designation?
d
If the l value is 3 what is the letter designation?
f
What can the values of Magnetic Quantum number be?
integers from -l to +l
when l = 0 what are the possible ‘m sub l’ values?
0
when l = 1 what are the possible ‘m sub l’ values?
-1,0,1
when l = 2 what are the possible ‘m sub l’ values?
-2,-1,0,1,2
when l = 3 what are the possible ‘m sub l’ values?
-3,-2,-1,0,1,2,3
What is the spin behaviour of an electron?
+1/2 or -1/2
How do you indicate the electron spin movement?
by a half arrow (⇀ )
In the atomic spectra when an electron is excited what does it do?
transitions from an orbital in a lower energy level to an orbital in a higher energy level
In the atomic spectra when an electron is relaxed what does it do?
transitions from an orbital in a higher energy level to an orbital in a lower energy level
What is the equation for total electron energy?
= -2.18 x 10^-18 J ((1/N^2f) - (1/n^2i)) f=final state i=initial state
What is a node? (atomic spectra)
areas of no probability of electron occurring
