Karteikarten
quantum theory
Karten in diesem Stapel (23)
- 1electromagnetic radiationa form of energy transmission in which electric
and magnetic fields are propagated as waves through empty space (a vacuum)
or through a medium, such as glass. - 2unit of wavelength (cm, um, nm, a, pm)cm 10-2
10--6
10-9
10-10
10-12 - 3speed of lightA distinctive feature of electromagnetic radiation is its constant speed of
in a vacuum, often referred to as the speed of light.
2.99792458 * 108 m s-1 - 4order of frequenceradio< micro-wave< infrared< visible (in between infra-red to ultraviolet)< utraviolet< x-rays< gamma rays
- 5unit of hertskhz 10^3
mhz ^6
giga hz ^9 - 6photoelectric effectnumber of e- emitted depends on the intensity of the incident light
KE fo the emitted e depend on the frequency of thelight
(vs is not inflenced by intensity - 7emission spectroscopybright lines are observed on a dark background of the photographic plate
- 8absorption spectroscopydark lines are observed on a bright background of the photographic plate.
- 9steps of proving the uncertainty principle intepreted graphicallya collection of waves with varying wavelength can combine into a wave packet. the superposition of the different wavelength yields an average wavelength and causes the wave packet to be more localized (delta x). the greater the no of the wavelengths that combine, the more precisely the particles can be located (ie. smaller delta x). -> since each of the wavelength corresponds to a different value of momentum according to the de brogile relation, the greater is the uncertainty in the resultant momentum (delta p)
- 10why Bohr model is incorrect?Borh only postulates only certain allowed circular orbits for the electron. experimentally, the bohr cannot explain the emission spectra of atoms and ions with more than one electron. fundamentally, the postulate of quantized angular momentum forcing an electron into a circular orbit has no bases. (limitation)
but is incorrect because an electronn cannot be constrained to a 1-d orbital (1-d in the sense that the e- cannot move off a circular path of a fixed radius)
with the proof of wave particle duality and uncertainty principle - 11what we canf understnd from wave function and n?-you should be able to prove this.
-> energy cannot be zero. (n=1 is the lowest possible energy (zero-point energy)
-> as size of box (L) decreases kinetic energy increases and hence momentum decreases (uncertainty principle).
With a larger kinetic energy, the velocity of the particle (u) would be higher. As momentum (p) is the product of mass and velocity (mu), the particle’s momentum would get larger when the particle has a higher velocity. According to the uncertainty principle, the momentum of the particle with a higher velocity will be more uncertain, that is Dp is larger when u is larger (because Dp = mDu). So it is the knowledge of the momentum decreases, but NOT the momentum itself decreases, when the particle has a larger kinetic energy which is caused by a decrease in L in this case. - 12quntum numbers and electron orbitals-principle quantum number: size and energy of orbitals. (the higher the value of n, the greater the electron energy and the the farther, on average, the electron is from the nucleus)
-angular momentum quantum number: shape of atomic orbitals (sometimes called subshell) : the numer of subshells in a principal shell is the same as the number of allowed values of the l)
-magnetic quantum number: orientation of the orbital in space relative to the other orbitals in the atom
(the number of orbitals in a subshell is the same as the number of allowed values of ml for the particular value of l) - 13three quantum number describes electron orbitals. there is one more. (fourth quantum number)there are two possibilities for electron spin and this requires a 4th quantum number, electron spin quantum number.
+1/2, -1/2
two possibilities for electron spin are shown with their associated magnetic fields. two electrons with opposing magnetic fields that cancel, leaving no net magnetic field for the pair. - 14energy of orbitls in a single electron atom(diagram should be provided)
-in a hydrogen atom, for example, all orbitals with the same principal quantum number (n) are degenerate (of the same energy level). since hydrogen has no repulsion between e- because only one e- is present. - 15energy orbitals in a multi-electron atomin multi-electron atoms, the attractive force of the nucleus for a given electron increases as the nuclear charge increases. as a result, the orbital energy become less (more negative) with larger atomic number of the atom. also, orbital energies in multi-electron atoms depend on the type of orbitals. the orbitals with different values of l within a principal shell are not degenerate.
- 16penetration and shielding-e- in orbitals closer to the nucleus screen or shield the nucleus from electrons farther away.
- the screening electrons reduce the effectiveness of the nucleus in attracting the particular more-distant electron, reducing the nuclear charge the outer electron feels.
- the electrons in s orbitals are more effective at screening the nucleus from outer electrons than are electrons in p or d orbitals.
- the ability of electrons in s orbitals that allows them to get close to the nucleus is called penetration.
screening ability: s>p>d
penetrationg ability: s>p>d
s is the most compact with electron density. - 17electron configuration. rules for assigning electrons to orbitals.aufbau principle:According to the principle, electrons fill orbitals starting at the lowest available (possible) energy levels before filling higher levels (e.g. 1s before 2s). The number of electrons that can occupy each orbital is limited by the Pauli exclusion principle (electrons occupy orbitals in a way that minimizes the energy of the atom.)
pauli exclusion principle: NO two electrons in an atom can have the same four quantum numbers :the two electrons in the same orbital must be antiparallel-
- hund's rule: electrons will fill in orbitals of equivalent energy in such a way that as many spins remain unpaired and is parrallel way as possible. - 18two exceptions for aufbau process.cr and cu.
special stability for configuration in which a 3d subshell is half filled with electrons (As with cr) or completely filled (As with cu) - 19atomic radii periodic trends.-down a group, atomic radii increase with the additioin of sucessive electron shells (n increases)
-across a period: atomic radii decreases
electrons are added to the same quantum shell of the atom. -> ineffective shielding, effecting nuclear charge increases, atoms become more compact. - 20ionization energy trends.ionization energy is the quantity of energy a gaseous atom must absorb to be able to expel an e-.(more energy is needed to move an e- away from an ion with +charge)
-ionization energies decrease as atomic radii increase. generally, increase from lower left corner of periodic table to the upper right corner.
(1) more energy is required to ionize noble gas atoms than to ionize atoms of the elements immediately proceding or following them. the maxima on the graph come at the atomic numbers of the noble gases.
(2) the alkali metals are the most easily ionized of all groups. the minima in the graph come at their aomic numbers.
for each atom (indivisual) extra stability is needed when full-filled subshell, half-filled subshell,, full-filled quantum shell.
(conclusion (dont know its valid): other than the principal quantum shells, there are also subshells comprising the electronic structure. - 21electron affinity to gain an electron.when a nonmetal atom gains a secnod electron, electron affinity values are positive because the electron is to be added to a negative ion. there is strong repulsion.
- 22reflection of the colorred light is refracted the least.
violet light the most - 23dual nature of lightelectromagnetic radiation exhibits
wave properties, particle properties
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- Beschreibung
- chemistry Karteikarten am quantum theory, erstellt von SEOLAH KIM am 13/05/2015.
- Erstellt von
- SEOLAH KIM
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