Rutherford’s model of the atom
-concept of nuclear atom
-bombarded metal foil with alpha
particles and showed that the nucleus
has protons and neutrons and was
small compared to the rest of the atom
-see Rutherford transparency
-positive alpha particles were deflected
when they were close to the positive
center of the atoms
Energy and light
-energy or radiation exhibits wave like
behavior and travels through space at
the speed of light in a vacuum and
includes the electromagnetic spectrum
-provides means of energy transfer
Longshort wavelengths
radio-microwave-infrared-visible-ultraviolet-x-rays-gamma
?What happens to the frequency as the
wavelength increases?
-as wavelength of light increases then
frequency decreases
photons-stream of tiny packets of
energy that can be a beam of light
traveling through space
emission of energy by atoms
-when salts containing certain ions are
set on fire-brilliant colors are emitted
-heat from a flame causes the atoms to
absorb energy and the electrons
become excited and move to a higher
energy level
-the excess energy is released in the
form of light as the electron moves to a
lower energy state, it emits a photon of
light
-different types of atoms emit different
colored light because different
wavelengths of light carry different
amounts of energy per photon
-red has less energy as red has longer
wavelength
Wavelength-distance between two
consecutive wave peaks
-different wave lengths carry different
amounts of energy
EX: red light photons carries less
energy than photons of blue light
Frequency
-indicates how many wave peaks pass
a certain point per given time period
-Short wavelength=higher frequency
-Long wavelength=lower frequency
Wavelength-distance between two
consecutive wave peaks
-different wave lengths carry different
amounts of energy
EX: red light photons carries less
energy than photons of blue light
Frequency
-indicates how many wave peaks pass
a certain point per given time period
-Short wavelength=higher frequency
-Long wavelength=lower frequency
11.4 energy levels of hydrogen
-ground state-lowest possible energy
state of an atom
-energy contained in the photon
corresponds to the change in energy
that the atom experiences
There are four excited states in
hydrogen that can exist in any of these
states and can undergo energy changes
to the ground state
-we study the photon as visible light
emitted as we see only certain colors as
only certain types of photons are
produced from each element
-that fact proves that only certain
energy changes occur and that atoms
have certain discrete energy levels
-quantized is the word we use saying
that only certain values are allowed
-we use to believe that electrons could
exist at any energy level having a
continuous set of energy levels
Analogy of a ramp that varies
continuously in elevation to a flight of
stairs that allows only certain
elevations begin quantized is similar to
the quantized energy levels of an atom
Bohr’s model of the atom
Neils Bohr-1911 received his Ph D in
physics
-was convinced that an atom has small
positive nucleus with electrons
orbiting around it like the planets
orbit the sun
-suggested that electrons could jump
to a different orbit by absorbing or
emitting a photon of light with exactly
the correct energy content = the
difference between the orbitals
-incorrect as electrons don’t move in
circular paths and the line spectrum
ONLY worked for hydrogen BUT
paved the way for future theories
Wave mechanical model of the atom
Schrodinger-electrons may have wave
and particle characteristics
-electrons move in orbitals NOT orbits
-can mathematically only predict the
probability of finding an electron at a
given point in space around the
nucleus
-NO information about when an
electron is in a given point in space or
how it moves
11.7 hydrogen orbitals
Orbital-representation of the space
occupied by an electron
-probability of finding an electron
decreases with greater distance from
the nucleus but NEVER becomes 0
-edge of orbital “fuzzy” so no defined
size
-electrons spend 90% time in orbital
sphere
Hydrogen energy levels
Principle energy levels-discrete energy
levels labeled with integers and
subdivided into sublevels
?In a hydrogen atom, an electron
undergoing which of the following
transitions would emit light of the
shortest wavelength?
n= 5 to n=1 or from n=4 to n=1
n=5 to n=1 because greatest distance
back to ground state-probably would
be blue or green light-higher energy
Level 1 = sublevel (1s)
Level 2 = 2 sublevels (2s,2p)
Level 3 = 3 sublevels (3s,3p,3d)
Level 4 = 4 sublevels (4s,4p,4d,4f)
Letters tell you the shape
s=spherical
p=2 lobbed
d=more than 2 lobes
x,y,z = tells along which coordinate the
two lobes lie
-shape does not tell you about electron
movement
Hydrogen orbitals
-hydrogen has 1 electron but three
energy levels
-at ground state, it lies in the 1s orbital
but can be excited to the 2s or 2p
orbital
Pauli exclusion principle
-electrons that have the same spin
cannot occupy the same orbital-they
must have opposite spins and an
orbital can only hold two electrons
11.9-11.10
Electron configuration
-electron arrangement
-most attractive orbital to an electron
in an atom is the 1s because it is closer
to the positively charged nucleus
Orbital or box diagram
-orbitals are represented by boxes
grouped by sublevels(s,p,d,f) with
small arrows indicating electrons
-remember to use opposite spins
Valance electrons-electrons in the
outermost(highest) principal energy
level of an atom and are the most
important electrons to a chemist
because they are the one involved with
bonding electrons
Core electrons-inner electrons NOT
involved in bonding atoms(they exist
in a a full energy level)
-atoms of elements in the same group
have the same number of electrons in
a given type of orbital
?How many electrons can be in the 3d
sublevel?
ten
Atomic properties and periodic trend
General
-chemistry is based on observed
properties of substances
-atomic theory is an attempt to help us
understand how these things occur so
we can better control the chemical
events that are so important in our
lives
-properties of elements and trends that
occur in these properties help us
understand observed behavior of
matter
Metals vs nonmetals
-metals-lustrous, malleable,
conductors (sea of electrons)
-nonmetals- opposite properties
-chemical differences between metals
and nonmetals occur because metals
tend to lose electrons and nonmetals
tend to gain electrons from opposite
charges
-not all metals act exactly alike as
some metals give up electrons easier
than others
Cs>Rb>K>Na>Li
-down the group electrons are given
up easier as they are further from the
nucleus as Cesium’s valance electrons
is in group 6s
-most active metals in lower left hand
corner(Cs) and most active nonmetals
in upper right(F) hand corner where
electrons pulled away from metals the
easiest
Atomic size
-down a group as energy levels
increase as electrons distance from
nucleus increases size increases
-across a period electrons are in outer
most energy levels are in same
principle energy level but as numbers
of protons increases pulling electrons
into them
?Which is the smallest atom in group
6?
oxygen
Ionization energy
-the energy required to remove an
electron from an individual atom in
the gas phase
-metals are low as it takes little energy
to remove their valance electrons
-down a group this energy decreases so
lowest energy in the lower left hand
corner(easier to pull off at bottom)
-nonmetals have HIGH ionization
energy and so the highest is the top
right hand corner(F)
?Which of the following have the
highest ionization energy?
K, Si, or O
-oxygen
?How did you know?
Closest to fluorine(highest energy)