Download Chemistry Electrons in Atoms Outline

Arrangement of Electrons in Atoms
I.
DEVELOPMENT OF A NEW ATOMIC MODEL
A. Wave nature of light
1. light is part of the electromagnetic radiation spectrum
2. light is a wave
i.
light has a wavelength  and frequency 
ii.
these are related to the speed of light c = 
iii.
speed of light = wavelength x frequency
3. the speed of light is a constant 3.00 x 108 meters/second (or m/s)
B. the electromagnetic spectrum includes wavelengths that are smaller than the visible
spectrum (gamma rays, X-rays and Ultraviolet light)
C. the electromagnetic spectrum includes wavelengths that are larger than the visible
spectrum (infared, microwave, AM-radio, FM-radio and TV)
D. Particle nature of light
1. the photoelectric effect supports the particle theory of light
2. when light of the correct frequency shines onto metal, an electron is ejected from the
metal
3. Quantum of energy = the minimum amount of energy that can be lost or gained by an
atom
4. E = hMaxwell Planck’s equation relating energy with frequency
i.
E = energy
ii.
h = Planck’s constant 6.626 × 10-34 J*s
ii.
 frequency
iii.
HERTZ is the unit for frequency
Hz = Hertz = 1/seconds = s-1
MHz is Mega Hertz = Hz x 106
FM radio frequency range is 88 MHz to 108 MHz
KHz is Kilo Hertz = Hz x 103
AM radio frequency range is 535 kHz to 1700 kHz
iv.
Meters is the unit for wavelength
Meters = m
nm = nanometer = m x 10-9
5. Photon is a particle of light that has zero mass and carries a quantum of energy
E. Hydrogen atom line-emission spectrum
1. When electricity is passed through hydrogen gas in a vacuum tube, the gas glows and
this light can be passed through a prism (or spectroscope) and individual lines are
produced NOT a rainbow spectrum of all colors
2. This line spectrum supports the particle theory of light
3. Electron in a ground state = lowest energy state for the electron
4. excited state = after the electron absorbs energy, the electron is in a higher energy level
than the ground state
5. line spectrum are found in the visible light range, the ultraviolet (UV) range, and the
infrared range of electromagnetic spectrum
6. When an electron falls from an excited state to a lower state it emits a photon of light
(particle of light)
F. BOHR MODEL OF THE HYDROGEN ATOM
1. Bohr model is based on planets orbiting around the sun
2. The electron orbits around the nucleus but ONLY at certain “allowed” orbits
3. An electron will absorb photons of light in order to move from a ground state to an
excited state
4. An electron will emit photons of light when it moves from a higher energy level (excited
state) to a lower energy level
5. atoms emit light when the electrons move from higher to lower energy states
II.
THE QUANTUM MODEL OF THE ATOM
A. Electrons as waves
1. we can think of light as a wave or a particle
2. we can think of an electron as a particle or a wave
3. Louis DeBroglie was the first to suggest the wave nature of the electron
4. the electron energy can be calculated using the equation E = h
5. diffraction patterns produced by electrons passing through a substance are similar to
diffraction patterns of light passing through a small hole
B. Heisenberg Uncertainty Principle
1. we cannot tell the position and the momentum of an electron simultaneously (at the
same time)
2. by observing an electron with light we actually change the electron’s position or its
momentum
C. Schrodinger Wave Equation
1. this equation describes mathematically the wave properties of electrons and other very
small particles
2. atomic energy levels, sublevels and orbitals describe where we will most likely find an
electron in a region around the nucleus of an atom
3. ENERGY LEVELS-all atoms have different energy levels like the Bohr model of the
hydrogen atom
4. The ROWS of the periodic table represent the highest occupied energy level of the
electrons in the atom
5. There are energy levels 1, 2, 3, 4, 5, 6 and 7 for the ground state electrons
6. SUB-SHELLS or SUBLEVELS -each energy level is separated into different sublevels s, p,
d, and f
i.
the first energy level only has an s sublevel
ii.
the second energy level has s and p sublevels
iii.
the third energy level has s, p and d sublevels
iv.
the fourth energy level has s, p, d and f sublevels
v.
the fifth energy level has s, p, d, and f sublevels
vi.
the sixth energy level has s, p, d, and f sublevels
vii.
the sublevels are represented by the different “block” regions of the periodic
table
7. ORBITALS- each sublevel is split into different numbers of orbitals
i.
Each orbital can have a maximum of two electrons
ii.
the “s” sublevel has one orbital and is in the shape of a sphere
iii.
the “p” sublevel has three orbitals and is in the shape of a dumbbell
iv.
the “d” sublevel has five orbitals
v.
the “f” sublevel has seven orbitals
III.
ELECTRON CONFIGURATIONS
1. Aufbau Principle states an electron occupies the lowest-energy orbital that can receive it
(electrons are filled from the lowest energy levels to the highest energy levels)
2. Pauli exclusion principle states no two electrons in the same atom can have the same set
of four quantum numbers
i.
we cannot have two electrons with the same spin in the same orbital
ii.
two up arrows cannot be in the same box of an orbital notation diagram
iii.
two down arrows cannot be in the same box of an orbital notation diagram
3. Hund’s Rule states orbitals of equal energy are each occupied by one electron before any
orbital is occupied by a second electron
4. Orbital notation represents electrons as arrows and orbitals as boxes
5. Electron configurations eliminates the boxes and arrows of orbital notation and uses
numbers letters and superscripts to represent electrons
6. 1s2 represents the first energy level the “s” sublevel occupied with 2 electrons
7. Noble gas configurations are a shortened version of the electron configuration which uses
the noble gas to represent filled sublevels of the inner electrons
8. Valence electrons are outer shell electrons that occupy the highest energy level in the
atom