Chapter 6 Flashcards
Describes the theory that James Clerk Maxwell developed.
James Clerk Maxwell developed a mathematical theory to describe light and other forms of radiation in terms of oscillating, or wave like, electric and magnetic fields
Electromagnetic radiation is characterized by its _________ and____________.
Electromagnetic radiation is characterized by its wavelength and frequency
What is the definition of wavelength and its symbol?
Symbolized by greek letter lambda λ
Defined as the distance between a given point on a wave and the corresponding point in the next cycle of the wave.
What is the definition of frequency, its symbol and the unit?
Symbolized by the greek letter nu (ν)
Refers to the number of waves that pass a given point in some unit of time, usually per second.
The unit for frequency, written either as s^(-1) or 1/s and standing for 1 oscillation per second, is called a hertz
To what wavelength and frequency is related to?
Wavelength and frequency are related to the speed (c)
How do we calculate the speed (c) with wavelength and frequency?
c (m/s)= λ(m) X ν(1/s)
electromagnetic radiation consists of ____________ and ______________
electromagnetic radiation consists of oscillating electric and magnetic disturbances
Wavelength-Frequency conversions
The frequency of the radiation used in cell phones covers a range from about 800MHz to 2GHz. (MHz stands for “megahertz”, where 1 MHz= 10^6 1/s; GHz stands for “gigahertz”, where 1 GHz = 10^9 1/s)
The value of the speed of light is: 2.998 X 10^8 m/s
What is the wavelength (in meters) of a cell phone signal operating at 1.12 GHz?
Example 6.1: Chemistry and chemical reactivity 9th edition Student book.
λ= c 2.998 X 10^8 m/s
— = ————————— = 0.268m
v 1.12 X 10^9 1/s
What is the value of the Planck’s constant?
6.6261 x 10^-34 J∙ s
What Max Planck assumed in his experiment?
Assumed that only certain vibrational energies were allowed, and they are related to the frequencies emitted by Planck’s equation:
E (J) = h (J∙s) x ν (s^-1)
Where h=6.6261 x 10^-34 J∙ s
What happens if an oscillator changes from a higher energy to a lower one?
Energy is emitted as electromagnetic radiation, where the difference in energy between the higher and lower energy state is
∆E= E(higher n) - E(lower n) = ∆nhν
What is the Planck’s equation?
E=hν
Where h is the Planck’s constant
v is the frequency
What is the key aspects of Planck’s theory for general chemistry ?
The key aspects of Planck’s theory for general chemistry are that Planck introduced the idea of quantized energies and the equation E=hv, an equation that was to have an important impact on the work of Albert Einstein in explaining another puzzling phenomenon.
Which ideal Planck introduced?
The idea of quantized energies
In which explanation Albert Einstein incorporated Planck’s ideas?
Albert Einstein incorporated Planck’s ideas into an explanation of the photoelectric effect.
What is the Einstein photoelectric effect?
The photoelectric effect is the observation that many metals emit electrons when light shines upon them.
Einstein characterized the Photons, as packets of energy, and stated that the energy of each photon is proportional to the frequency of the radiation as defined by _______________
Einstein characterized the Photons, as packets of energy, and stated that the energy of each photon is proportional to the frequency of the radiation as defined by Plank’s equation.
Energy and chemistry: using Planck’s equation
DVD players use laser that emit red light with a wavelength of 640nm.
What is the energy of one photo of this light? What is the energy of 1.0 mol of photons of red light?
1 photons = 6.022 X 10^23 photons= Avogadro’s number
Example 6.2: Chemistry and chemical reactivity 9th edition Student book.
The wavelength (640nm) expressed in meters id 6.4 X 10^-7 m. The frequency is determined using the wavelength- frequency equation
λ= c 2.998 X 10^8 m/s
— = ————————— = 4.7 X 10^14 1/s
v 6.4 X 10^-7 m
Then the frequency is used to calculate the energy per photon.
E=hν
E per photon = hv=
(6.626 X 10^-34 J∙s/photon) X ( 4.7 X 10^14 1/s)
= 3.1 X 10^-19 J/photon
The energy of a mole of photons is calculated by multiplying the energy per photon by Avogadro’s number
E per mol =
(3.1 X 10^-19 J/photon) X (6.022 X 10^23 photons)
=1.9 X 10^5 J/mol
in which condition an atom in gas phase is said to be “excited”?
If a high voltage is applied to atoms of an element in the gas phase at low pressure, the atoms absorb energy and are said to be “exited”.
The exited atoms can then emit light.
What Johann Balmer and Johannes Rydberg has found ?
Johann Balmer and Johannes Rydberg has found and equation named Balmer equation to calculate the wavelength of the red, green, and blue lines in the visible emission spectrum of hydrogen
1/λ= R((1/2^2) - (1/n^2 ))when n >2
n is an integer
R is Rydberg constant with the value 1.0974 X 10^7 m^-1
Which model Bohr proposed?
Bohr proposed a model for the electronic structure of atoms and with it an explanation for the emission spectra of excited atoms.
Bohr proposed a planetary structure for the hydrogen atom in which the electron moved in a circular orbit around the nucleus, similar to a planet revolving about the sun.
What is the equation that Bohr proposed in his model of the hydrogen atom ?
E_n= - (Rhc)/n^2
E_n: is the energy of the electron (in J/atom) R is the Rydberg constant H is Planck’s constant C is speed of light n^2 is the principal quantum number
What Louis Victor de Broglie proposed ?
Louis Victor de Broglie proposed that a free electron of mass m moving with a velocity ν should have an associated wavelength λ, calculated by this equation.
λ=h/mv
What Erwin Schrodinger developed?
He developed a model for electrons in atoms that has come to be called quantum mechanics or wave mechanics.
What the wavefunction for an electron in an atom describes ?
The wavefunction for an electron in an atom describes an atomic orbital
Each orbital is described by 3 quantum numbers, state them.
n
l
m_l
Which quantum number is the principal one?
n is the principal quantum number
What can be the values of the quantum number n?
The principal quantum number n can have any integer value from 1 to infinity. The value of n is the primary factor in determining the energy of an orbital.
What the quantum number n defines?
It define the size of an orbital: the greater the value of n, the greater the size of the orbital
How do we call the quantum number l?
the orbital angular momentum quantum number
What is the value of l is n=0?
l=s
What is the value of l is n=1?
l=p
What is the value of l is n=2?
l=d
What is the value of l is n=3?
l=f
How do we call the quantum number m_l
the magnetic quantum number
The quantum number m_l is related to ______________________________________
m_l is related to the orientation in space of the orbitals within a subshell.
To which quantum number a 1s orbital is associated with?
n=1 and l=0
What is the shape of s orbitals?
spherical shape.
to see it: http://study.com/cimages/multimages/16/s_orbital_1.png
What is the shape of p orbitals?
dumbbell shapes
to see it:
https://np-apchemistry.wikispaces.com/file/view/p_orbitals.JPG/77400425/p_orbitals.JPG
To which quantum number a 1p orbital is associated with?
l=1
To which quantum number a 1d orbital is associated with?
l=0
What is the shape of a d_xy orbital?
lies in the xy-plane
2 nodal surfaces are the xz and the yz planes.
to see it: http://study.com/cimages/multimages/16/d_orbital1.png
What is the shape of a d_xz and d_yz orbital?
lie in planes defined by the xz and yz axis
have 2, mutually perpendicular nodal surfaces
to see it: http://study.com/cimages/multimages/16/d_orbital1.png
What is the shape of a d_x^2 y^2 orbital?
easier to visualize
the nodal planes bisect the x and y axes
the region of electron density lie along the x and y axes
to see it: http://study.com/cimages/multimages/16/d_orbital1.png
What is the shape of a d_z^2 orbital?
has 2 main regions of electron density along the z axis.
a “doughnut” of electron density also occurs in the xy plane
2 cone-shaped nodal surfaces.
to see it:
http://study.com/cimages/multimages/16/d_orbital1.png
What was the experiment of Otto Stern and Walther Gerlach ?
Otto Stern and Walther Gerlach performed an experiment that probed the magnetic behaviour of atoms by passing a beam of silver atoms in the gas phase through a magnetic field
