chapter 7 Flashcards
how was the behavior of matter seen before the 20th century?
deterministic (present set of conditions used to predict future behavior)
are subatomic particles really deterministic?
no, the act of measuring/observing very small particles affects the system in unpredictable ways
what are quantum mechanics?
a set of guidelines subatomic particles follow
what is wave particle duality? does light have it?
a concept that every quantum entity can be described as either a particle or a wave. yes.
what is electromagnetic radiation?
the energy created from oscillating electric and magnetic fields that are perpendicular to each other
what is amplitude? determines?
height of trough, determines the intensity of the waves
what is wave length? what does it determine?
distance between two troughs/crests in the visible spectrum. determines the color
what is frequency?
the number of cycles that pass through a stationary point in a given period of time (Hertz, cycle per second)
formula for frequency
c (velocity of light) / wavelength
what does EM span from?
10^-6 m (gamma rays) to 10^5m (radio waves)
what is photoelectric effect?
the observation that metals can emit electrons when light shines upon them. classic EM theory could not account for it
what did einstein predict about light?
it is quantized, meaning light energy is delivered in packets called quanta or photons
what is the energy of a photon proportional to?
its frequency
what is the proportional constant?
proportionality constant is called Planck’s Constant, (h) and has the value 6.626 x 10−34 J∙s
how can orbits exist within bohrs model?
• Each of these orbits could only exist at a specific, fixed distance from the nucleus
what two things are the energy of orbits?
quantized or fixed, and proportional to the distance from the nucleus
how is the energy of orbits ranked in relation to the nucleus?
- orbits closer to the nucleus are lower in energy than those further away,
- En=1 < En=2
(hydrogen atom) what is the lowest energy orbit called?
n=1, the ground state
how can an electron go into excited state?
electron absorbs energy equal to the energy difference between orbits
what happens if enough energy is absorbed?
electron can be ejected from hydrogen
(atomic spectra) how long does the excited state last?
very short lifetime
what happens when the electron relaxes to ground state
light is emitted
emitted light has the same energy as ______?
absorbed energy
what did analogy with the photoelectric effect suggest?
suggested the light emission originated with the electrons in atoms. This suggests that an electron in an atom can only have certain energies - the electron energy levels are quantized
equation for transitions in HYDROGEN
ΔEelectron = Efinal state − Einitial state
where does an electron move when energy is emitted? is delta E positive or negative?
closer to the nucleus, s (nfinal>ninitial), so ΔE is positive
when an atom absorbs energy where does it move? is delta E positive or negative?
electron moves further from the nucleus (nfinal>ninitial), so ΔE is positive
small energy to big energy means?
absorption (usually)
what are the three problems with bohrs model?
○ Could not explain the emission spectra of multi electron elements
○ Electrons do not move in fixed orbitals
○According to classic physics electrons should emit ER and collapse into the nucleus
what did Louis de Broglie suggest?
Wave particle duality ;suggest that if energy is particle like, perhaps matter is wavelike
• Electrons interfering with themselves
what is the Heisenberg Uncertainty Principle?
you cannot observe the particle and wave nature of an electron at the same time
what is position?
particle nature
what is velocity?
wave nature
what is probability distribution?
electrons wont always hit the same place (five hole)
what is the Schrodinger equation? what does the answer give us?
• Solutions to the equation for a hydrogen atom yields many different solutions
The resulting functions are used to generate 3D plots to describe where an electron is found
how can standing waves exist?
A standing wave can also exist in a circular form.
Like linear standing waves, only certain wavelengths are allowed
what did Broglie and Schrodinger about Bohr’s model?
the Bohrs allowed electron orbits were the ones that could contain an integral number of wavelengths. • Other orbits produce destructive interference, and do not exist
what is a set of quantum numbers used for?
A set of three quantum numbers is used to describe each orbital
what is the principal quantum number? what does it describe?
n: describes the size and energy of the orbital
what is the angular momentum quantum number? what does it describe?
l: describes the shape of the orbital
what is the magnetic quantum number? what does it describe?
ml: describes the 3D orientation of the orbital
what is the magnetic spin number?
ms: describes the direction of electron spin; clockwise or counterclockwise
what numbers can n be? what happens as n gets larger?
N can be any integer greater than or equal to 1, the larger the more energy. the space between orbitals becomes smaller.