Title: Chapter 4 Arrangement of Electrons in Atoms
1Chapter 4Arrangement of Electrons in Atoms
2Light can act as a ______________.
? wavelength (lambda) ? frequency
waves/sec (nu), measured in Hertz, Hz 1/s
3c ? ?
- c speed of light (3.0 x 108 m/s)
- What is the frequency of a beam of red light
whose wavelength 659 nm?
4_________ _____________ is the only
electromagnetic (EM) radiation we can see
- electromagnetic radiation (EM) form of energy
that travels through space as a __________
5Light can also act as a ____________
- Supported by 2 experiments
- Photoelectric effect
- Hydrogen atom spectrum
6Particle description of light
- Max Planck, 1900 studied ___________ of light
by hot objects - Proposed that energy is not ____________
continuously but in small little ___________
called _____________ This is a particle
property - quantum min amt of energy than can be lost or
gained by an atom - Energy ? _______________
7Planck proposed the following relationship
between a quantum of energy and its frequency of
radiation
- Energy ? frequency
- E ( frequency )
- where h Plancks constant
- 6.626 x 10-34 J s (or J/Hz)
8Duality of light explained photoelectric effect!
Metal must be struck by a photon possessing a
min. amt of E below this amt, the electron
wont leave the metal! More light of the same E
(same ?) just released more electronsnot more
energetic
9- Ground state atoms whose electrons are in their
___________ energy level - Excited state an atom,having __________ E, jumps
its electron(s) to a higher E level. The electron
must jump completely from one level to another.
10- De-excitation after a short time the electron
____________________________ and _____ a photon
(packet of E) equivalent to the energy difference
between the 2 steps. The photon will produce a
spectral line with a discrete wavelength (color)
associated with it. - Continuous spectrumall wavelengths are present
(i.e.sunlight) - Emission (bright line) spectrum limited of
specific bright lines that are produced by pass
the light emitted by an excited atom through a
prism
11- Absorption (dark line) spectrum light emitted by
an excited atom passes through a substance that
filters out certain wavelengths and thus produces
a spectrum with missing (dark) lines. - Bright lines of an emission spectrum are
_____________________ as the dark lines of an
absorption spectrum for a given element.
12Bohr Model of the Atom, 1913
- Studied the absorption of light by ___________
- Absorption of light at definite wavelengths
corresponds to the definite changes in the E of
the _______________ - Electrons can circle the nucleus at ___________
_____________ distancesonly in allowed paths, or
orbits (Satellite model) - Energy of an electron is ____________ when it is
in orbits farther away from the nucleus - His calculated energy values agreed with the
observed spectral lines for hydrogen - Model did NOT work when applied to multi-electron
elements ?
13Duality of light
- Proposed by Einstein after studying the works of
Planck and Bohr - Light has been traditionally thought of as a
__________ (it has freq. wavelength) - But now.. light can also be thought of as a
__________ ___ ______ of particles called photons - photons particle of EM radiation having _______
mass and carrying a ______________ of energy - Explained photoelectric effect EM radiation is
absorbed only in whole numbers of photons
144-2The Quantum Model of the Atom
15De Broglie, 1924
- If light could behave as both a wave and a
particle, then could an electron (a particle)
also behave as both a particle and a wave
????????????? - He said _________ because.
- Since electrons could only exist at specific
energies, and E can be equated to frequency (E
h?), they have wave properties - And electrons can be focused like light
(electron microscopes) - particle nature of electrons had already been
confirmed (cathode rays, oil drop exper, etc.)
16- Electrons have a dual wave-particle nature
17Heisenberg Uncertainty Principle
- It is impossible to determine simultaneously both
the __________ and __________ of an electron or
any other particle
18Schrodinger Wave Equation, 1926
- If electrons have wave properties, then wave
equations can be applied to electrons (and other
small particles) - Laid foundation for __________ ___________
describes ______________________ the wave
properties of electrons and other very small
particles - Gives the ______________________ of finding an
electron at a given place in time around the
nucleus
19Quantum Theory (cont)
- Electrons do NOT travel around the nucleus like
planets around the sun - Electrons exist in certain regions called
______________ a 3-D region around the nucleus
that indicates the _________ location of an
electron
20Quantum Numbers
- Specify the properties of atomic orbitals and the
properties of electrons in orbitals - There are __________ quantum numbers.the first
three of which come from solutions to
Schrodingers wave equation
21Principal Quantum Number, n
- Indicates the _________ __________ _________
(or shell) occupied by the electron - n 1, 2, 3 etc.
- The ?n value, the ___________ the electron is
from nucleus? principal quant also gives
________ ________________ - Total electrons on a level __________
- Total orbitals on a level n2 since an orbital
can hold two electrons (2n2/2 n2)
22Angular Momentum Quantum Number, l
- Also known as second quantum number
- Also known as azimuthal quantum number
- Most energy levels (all but n1) have orbitals of
different __________, called ____________ - Describes the ______________ of the orbital
- orbital shapes possible is equal to the
- ______ _____________
- If n3, then there can be 3 orbital shapes
- The values of l 0, 1, 2,. (n-1)
- If n3, then l can be ___, ___, or ___.
23Angular Momentum Quantum Number, l (cont)
- An orbital LETTER is used to designate each
shape
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25Magnetic Quantum Number, ml
- also known as the 3rd quantum number
- indicates the orientation of an orbital around
the nucleus - (2 l 1)
26Magnetic Quantum Number, m (cont)
- Sum of all orbitals in a sublevel (or E level) is
a spherical cloud!
27Spin quantum number, s
- Describes the spin of the electron
- Could be either clockwise ( ½) or
counterclockwise (- ½ ) - Each orbital can hold a maximum of two electrons,
a pair, spinning in opposite directions
284-3
29Hunds Rule
- Orbitals of equal energy are ________ occupied by
one electron before any orbital is occupied by a
second electron, and - All electrons in singly occupied orbitals must
have the same _____
30Aufbau Principle
- An electron occupies the ________________ orbital
that can receive it
31Noble Gas Notation
- What is the noble gas electron notation for
calcium? - 1s22s22p63s23p64s2
- What is the noble gas config for S?
- 1s22s22p63s23p4
32PREDICTED