Chap 7

version from 2017-12-11 20:30

Section

define wavea vibrating disturbance by which energy is transmitted
characteristics of waveswavelength(l), amplitude, frequency(n), speed (u)
define Wavelength (l)the distance between identical points on successive waves
Frequency (n)the number of waves that pass through a particular point in 1 second
frequency and cycle equation1 Hz = 1 cycle/s
what does the speed of a wave (u) depend onthe type of a wave and the nature of the medium through which the wave is traveling (e.g. air, water, or vacuum)
equation for the speed of a waveu = l x n
units for u = l x n(u is m/s, l is m, n is Hz)
who and when proposed that visible light consists of electromagnetic wavesMaxwell 1873
components of electromagnetic wavean electric field component and a magnetic field component
compare and contrast the 2 components of electromagnetic wavesThe two components have the same wavelength, amplitude, frequency, and hence the same speed, but they travel in mutually perpendicular planes
what is the emission and transmission of energy in the form of electromagnetic waveselectromagnetic radiation
what is the speed of light (c) in vacuum 3.00 x 108 m/s
equation for all electromagnetic radiationl x n=c (wavelength x frequency = speed of light
The quantum theory developed by Planck successfully explainsthe emission of radiation by heated solids
Planck’s Quantum TheoryEnergy (light) is emitted or absorbed in discrete units (quantum)
Planck’s constant (h)= 6.63 x 10-34 J•s
E=hxnE=hxn E = h x c /l (n is the frequency of radiation, l is the wavelength of radiation )
Energy is emitted in whole-number multiples ofhn
Photoelectric Effect isa phenomenon in which electrons are ejected from the surface of metals exposed to light of at least a certain minimum of frequency
Light has bothwave nature and particle nature
Photon isa “particle” of light
hn = KE + WKE = hn - W (W is binding energy) (KE is the kinetic energy, W is the work function, a measure of how strongly the electrons are held in the metal)
Bohr’s Theory ofthe Hydrogen Atom
In bohr's model, light is emitted as e- moves fromone energy level to a lower energy level
In bohr's model, e- can only have specific(quantized) energy values
bohr model equationEsubn = - RsubH * 1/(n^2) n is (principal quantum number) = 1,2,3,…, RH (Rydberg constant) = 2.18 x 10-18J
which constant is used in bohr's modelRH (Rydberg constant) = 2.18 x 10^-18J
Ground state or levellowest energy state of a system (n = 1)
Excited state or levelhigher in energy than the ground state (n = 2, 3, 4…)
In the Bohr model, an electron emits a photon whenit drops from a higher-energy state to a lower energy state
equation for Photon, hn, absorbed or emittedDE = hn = RsubH * (1/n^2subi) - (1/n^2subf) n (principal quantum number) = 1,2,3,…
ni > nf: DE ispositive (Absorption) , ni < nf: DE is negative (Emission)
Calculate the wavelength (in nm) of a photon emitted by a hydrogen atom when its electron drops from the n = 5 state to the n = 3 stateEphoton = DE = RH (1/n^2subi) - (1/n^2subf)
LASERLight Amplification by Stimulated Emission of Radiation
De Broglie (1924) reasoned thatparticles such as e- have wave properties
De Broglie (1924) reasoned that an e- behaves like a standing wave in the atom, the length of the wave nl equalsthe circumference of the orbit 2pr (2pr =nl)
De Broglie extended Einstein’s wave-particle description of light toall matter in motion (l = h/(mu) ) u = velocity of e- (in m/s) m = mass of e- (in kg) h in J•s = 6.63 x 10^-34
The Heisenberg uncertainty principle states thatit is impossible to know simultaneously both the momentum (p) and the position (x) of a particle with certainty
The Heisenberg uncertainty principle equationDxDp >_ h/(4p) Dx= uncertainty in the position Dp = uncertainty in the momentum and p = m x v
Schrodinger’s equation can only be solved exactly for the _________. We must approximate its solution for _________hydrogen atom, multi-electron systems
In 1926, Schrödinger wrote an equation that describedboth the particle (m) and wave (Y) nature of the e-
Wave function (Y) describesenergy of e- with a given Y and probability of finding e- in a volume of space, Y2
an atomic orbital is a function () that defines the distribution of electron density (2) in space
Electron density gives the probability thatan electron will be found in a particular region of an atom
Quantum numbers describethe distribution of electrons in atoms; they are derived from the Schrödinger equation Y = fn (n, l, ml, ms)
letters in Y = fn (n, l, ml, ms)n = principal quantum number, l = angular momentum quantum number, ml =magnetic quantum number, ms = electron spin quantum number
Principal Quantum number (n)Main energy level (shell) and distance of e- from the nucleus
Angular Momentum Quantum number (l)Shape of the “volume” of space that the e- occupies
For a given value of n, l =0, 1, 2, 3, … n-1
Magnetic Quantum number (ml)Orientation of the orbital in space
For a given value of l ml = -l, …., 0, …. +l as inIf l = 1 (p orbital), ml= -1, 0, or1 If l = 2 (d orbital), ml= -2, -1, 0, 1, or2
Spin Quantum number (ms)Direction of the electron’s spin
ms = +½ or -½clockwise or not
how many orbitals does subshells s p d haveone 3 5
The total number of orbitals for a given value of n isn2
for s orbital, Its size increases asthe principal quantum number increases
position and shape of s orbitalspherical, centered in nucleus (only one)
only way the three p orbitals differ from each otherorientation
the five d orbitals are identical inenergy
what is l in s p d f orbitals0 1 2 3
In a single-electron atom, the energy of the electron is determined solely byits principal quantum number, n
In many-electron atoms, the energy of the electron is determined by its principal quantum number, n, ANDthe angular momentum quantum number, l
electrons with the same value of nshells
electrons with the same value of n and lsubshells
electrons with the same value of n and l and mlorbital
How many 2p orbitals are there in an atomIf l = 1, then ml = -1, 0, or +1 sp 3 orbitals (3 numbers of ml)
Pauli exclusion principleno two electrons in an atom can have the same four quantum numbers
Paramagnetic atoms areatoms with one or more unpaired electron spins; they are attracted by a magnet
Diamagnetic atomsare atoms in which all electrons are paired; they are slightly repelled by a magnet
hund's ruleevery orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin
Each subshell of quantum number l has (2l+1) orbitalsif l is 1 then 2+1=3 orbitals
aufbau principle states thatin the ground state of an atom or ion, electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels (e.g., 1s before 2s). In this way, the electrons of an atom or ion form the most stable electron configuration possible
either have incompletely filled d subshells or readily give rise to cations that have incompletely filled d subshellstransition metals
either have incompletely filled f subshells or readily give rise to cations that have incompletely filled f subshellsLanthanides or rare earth series