Transcript Ch4 notes - Midway ISD

Chapter 4
Arrangement of
Electrons in Atoms
4-1 The Development of
the New Atomic Model
• Rutherford’s atomic
model – nucleus
surrounded by fastmoving electrons- not
complete model
Wave Nature of Light
• Electromagnetic
Radiation- form of
energy that exhibits
wavelike behavior
• Ex: visible light,
microwaves, x-rays
• Electromagnetic
Spectrum- encompasses
all forms of EM radiation
Electromagnetic
Spectrum
• Wavelength (λ )- shortest
distance between
equivalent points on a
continuous wave
• Measured crest to crest
or trough to trough
• Frequency (ν )- number of
waves that pass a given
point per second
• 1 Hertz (Hz) = 1 wave per
second; SI unit of
frequency
• Amplitude- wave’s height
from the origin to a crest
or from origin to trough
• Speed of light =
wavelength x frequency
• C = λν
• Photoelectric Effectelectrons are emitted
from a metal’s surface
when light of a certain
frequency shines on the
surface
• Ex: calculator with
photoelectric cell
Particle Nature of Light
• Quantum conceptproduces glowing light of
hot objects
• Quantum- minimum
amount of energy that
can be gained or lost by
an atom
• Equantum = hv
• E = energy
• V = frequency
• h = Planck’s constant;
6.626 x 10-34 J•s
• J is joule; SI unit for
energy
• Photon- particle of EM
radiation with no mass
that carries a quantum of
energy
• Ephoton = hv
• Ground State- lowest
allowable energy state of
an atom
• Excited State- when an
atom gains energy
• Line Emission Spectrumset of frequencies of the
EM waves emitted by
atoms of the element
• Unique to each element,
used for identification
• Continuous spectrum
• Bohr Model of the Atomproposed that hydrogen
atom has only certain
allowable energy states
Sect. 4-2: The Quantum
Model of the Atom
• Electrons as waves…De Broglie
applies light’s wave-particle
duality to electrons/Bohr’s
model
• Heisenberg Uncertainty
Principle – impossible to know
position and velocity at same
time
• Schrödinger wave equation
• Quantum theory – describes
mathematically the wave
properties of electrons
• Orbital – probable location of
electron around nucleus
Atomic Orbitals and
Quantum numbers
• Quantum numbers – specify
properties of atomic orbitals
and electrons in orbitals
• solutions to Schrödinger wave
equation
• Principal quantum number (n) –
represents main energy level
(shell) & tells how many
sublevels
• Positive integers (1,2,3,etc.)
• Total # orbitals per shell = n2
• Total # electrons per shell =2n2
• Angular momentum quantum
number (l) – indicates shape
of orbital (sublevel)
• l = zero and all positive integers
less than or equal to n-1
• l=0, s orbital (spherical)
• l=1, p orbital (dumbbell)
• l=2, d orbital
• l=3, f orbital
• Magnetic quantum number (m) –
indicates the orientation of
orbital around nucleus
• range from -2 to +2, depending on
sublevels
• Spin Quantum number –
indicates spin state of electron
• can only equal ½ or -½
• orbital holds 2 max electrons &
they must have opposite spins
Sect. 4-3: Electron
Configurations
• Electron configuration –
arrangement of electrons in an
atom
Rules for Electron
Configurations
• Aufbau principle – lowest
energy level fills first
• Pauli exclusion principle –
electrons in same orbital,
opposite spin
• Hund’s rule – orbitals of equal
energy must all have 1
electrons before a second can
be added
• Orbital Notation (Diagram) –
lines, arrows, principal
quantum #, and sublevel
letter
• Electron Configuration
Notation – principal quantum
#, sublevel letter, and
superscript (# e-)
• Noble Gas Notation –
shortened version of
electron configuration
notation
• Deviations from normal electron
configurations (more stable
with pulling one from s to halffill or fill d)
• Chromium
• Copper