Chemistry Chap 5 Highlights
 Bohr’s Model of the Atom
1. Electrons move around the protons that are at
the center of the atom.
2. An electron in orbit has a fixed energy.
3. Electrons that are closer to the nucleus have
less energy than electrons that are more
distant from the nucleus.
 Quantum Mechanical Model of the Atom
1. Involves the probability of finding an electron
in a certain position.
2. Electrons’ energies are quantified by
A.Principal quantum numbers.
B. Energy sublevels.
C.Orbitals.
e.g. the second principal energy level
has two sublevels, 2s and 2p. 2s can
contain a maximum of two electrons
and 2p can contain a maximum of six
electrons. See Fig 5.7.
e.g. the third principal energy level
has three sublevels. 3s has one orbital
that can contain a maximum of two
electrons, 3p has 3 orbitals that can
contain a maximum of 6 electrons,
and 3d has 5 orbitals that can
contain a maximum of 10 electrons.
See Fig 5.7.
a) The orbitals fill by accepting one
electron in each orbital and only
then pairing up in the orbitals.
b) The maximum number of
orbitals in any single energy
level is
7 in the f sub level
c) The maximum number of
orbitals in the p sublevel is
3
d) The maximum number of
electrons in any sublevel is
found by multiplying the
number of orbitals by 2.
A.When an electron moves from a
lower energy level to a higher
energylevel it absorbs a quantum of
energy.
B. When electrons drop to lower
energylevels (quantum leaps)
a) Light is emitted
b) The greater the change in n,
the greater the change in
the energy of the light
emitted. The greater the
decrease in the energy level,
the greater the energy of
the emitted light.
c) The quantum of light
emitted is called a photon.
 Electron configuration symbols.
1. e.g. 4p3 means the electrons are
in the fourth energy level (principal
quantum number is 4), the electrons are
in the p shaped sublevel of quantum
number 4, there are 3 electrons in this p
sublevel.
 Shapes of atomic orbitals
1. The shape of the electron cloud is determined
by the electrons energy sublevel.
e.g. 3p is shaped like a dumbbell
 The number of electrons in any energy level can be
found by using the periodic table given to you.
1. The small numbers on the right hand side of
each element box indicate the number of
electrons in each energy level.
e.g. how many electrons are there in each
energy level of an: oxygen atom?
phosphorus atom?
sodium atom?
 Stable electron configurations are likely to contain
filled energy sublevels.
 Know how to determine the electron configuration
of any element by using Fig 5.7, p133.
1. Remember one electron goes in each orbital
before they pair up.
 Know how to find the number of unpaired
electrons.
e.g. how many unpaired electrons (half filled
orbitals) are there in a sulfur atom?
e.g. how many unpaired electrons are thee in a
bromine atom?
Electromagnetic Radiation (EMR)
 Includes
Radio waves
Radar waves
Microwaves
IR radiation
Visible light
UV light
X-rays
Gamma rays
 The speed of all electromagnetic radiation,
such as listed under EMR, in a vacuum is the
same (3x108m/s).
 The frequency ( f ) and the wavelength ( ƛ )
are related by the equation c = f ƛ ; where c =
3x108m/s, f is the frequency in Hz,
cycles/second, or s—1, and ƛ is the wavelength
measured in meters.
ƛ = c/f
The frequency and the wavelength of light
are related inversely (as one increases, the
other decreases and vice versa)
 As electrons drop more in energy levels, the
frequency( f ) of the atomic line spectra
emitted increases.
 For any particular kind of atom, the emission
spectra is the same throughout the known
universe.
e.g. the emission from hydrogen is the
same emission on Mars as it is on Earth,
et al.
 E = hf
 Know how to do simple algebra to find
unknown quantities.
 Quantum mechanics scientists and their
contributions.
Bohr
Defined an exact path of an electron
around a nucleus.
Louis de Broglie
Predicted that all matter can behave
as waves as well as particles.
Aufbau Principle
Electrons occupy the orbitals of
lowest energy first.
Heisenberg’s uncertainty principle
If the position of a moving particle is
known, its velocity cannot be known.