Ch 4 Section 2 Flashcards
Investigations into the photoelectric reflect and hydrogen a emission line spectrum revealed that
Light could behave as both a wave and a particle
French scientist Louis de broglie suggested that electrons be considered
Waves confined to the space around an atomic nucleus
It followed that the electron waves could only exist at
Specific frequencies
According to the relationship E= hv these frequencies corresponded to
Specific energies, the quantized energies of Bohr’s orbits
Electrons like light waves can be
Bent (diffracted)
Diffraction reefers to the
Bending of a wave as it passes by the edge of an object or through a small opening
Electron beams like waves can
Interfere with each other
Interference occurs when
Waves overlap
Overlapping results in a
Reduction of energy in some areas and an increase of energy in others
Heisenbergs proposal answers question of
Where electrons are located if they are both particles and waves
Heisenbergs idea involved the
Detection of electrons
Electrons are detected by their
Interaction with photons
Because photons have about the same energy as electrons any attempt to locate a specific electron with a photon
Knocks the electron off its course
The Heisenberg uncertainty principle stated that it is impossible to
Determine simultaneously both the position and velocity of an electron or any other particle
Heisenberg uncertainty principle is One of the fundamental principles of our
Present understanding of light and matter
In 1926 Austrian physicist Erwin schrodinger used the hypothesis that electrons have a dual wave particle nature and
Developed an equation that treated electrons in atoms as waves
To explain why atomic energy states are quantized scientists had to change
The way they viewed the nature of the electron
Quantization I’d electron energies was a natural outcome of
Schrodingers equation
Only waves of specific energies and therefore frequencies
Provided solutions to the equation
Together with the Heisenberg uncertainty principle the schrodinger wave equation laid the
Foundation for modern quantum theory
Quantum theory describes mathematically the
Wave properties of electrons and other very small particles
Solutions to the schrodinger wave equation are known as
Wave functions
Based on the Heisenberg uncertainty principle the early developers of quantum theory determined that wave functions give only the
Probability of finding an electron at a given place around the nucleus
Electrons do not travel around the nucleus in
Neat orbits as Bohr had postulated
Instead electrons. Exist in certain regions called
Orbitals
Am ornital is a
3d region around the nucleus that indicates the probably location of an electron
According to the schrodinger equation electrons in atomic orbitals also have
Quantized energies
An electrons energy level is not the only characteristic of an orbital that is indicated by
Solving the schrodinger equation
Quantum numbers specify the properties of
Atomic orbitals and the properties of electrons in orbitals
The first 3 quantum numbers result from
Solutions to the schrodinger equation. They indicate the main energy level shape and orientation of an orbital
The fourth, spin quantum number, describes a
Fundamental state of the electron that occupied the orbital
The principal quantum number symbolized by n indicated the
Main energy level occupied by the electron
Values of n are
Positive integers only
As n increases the electrons energy and its average distance from the nucleus
Increase
An electron for which n = 1 occupied the
First (lowest) main energy level and is located closest to the nucleus
More than one electron can have the same
N value. These electrons are sometimes said to be in the same electron shell
Total number of orbitals that exist in a given she’ll is
N^2
Except at the first main energy level orbitals of different
Shapes–known as sublevels– exist for a given value of n
The angular momentum quantum number symbolized by l indicates the
Shape of the orbital
For a specific main energy level the number of orbital shapes possible is
Equal to n
The values of l allowed are
zero and all positive integers less than or equal to n-1
Depending on its value of l an orbital is
Assigned a letter
S orbitals are
Spherical
p orbitals have
Dumb bell shapes
D orbitals are more
Complex
In the first energy level n=1
There is only one sublevels possible an s orbital
second energy level n=2 has
2 sublevels the s and p orbitals
In the nth main energy level there are
N sublevels
Each atomic orbital is designated by the
Principal quantum number followed by the letter of the sublevels
Atomic orbitals can have the same
Shape but different orientations around the nucleus
The magnetic quantum number symbolized by m indicated the
Orientation of an orbital around the nucleus
Values of m are whole numbers including
Zero from -l to +l
Because an s orbital is spherical and is centered around the nucleus it has
Only one possible orientation
S Orientation corresponds to a magnetic quantum number of
M = 0
Only one s orbital in each
Sublevels
The loves of a p orbital extend along the
X y or z axis of s 3 dimensional coordinate system
There are 3 p orbitals in each
P sublevel which are designation as px py pz
The 3 p orbitals occupy different regions of space and those regions are related to values of
M = 0 m = -1 m =+ 1
There are 5 different d orbitals in each
D sublevel
Five different orientations of d correspond to values of
M = -2. M = -1 m = 0 m= 2 m= 1
There are 7 different f orbitals in each
F sublevel
The total number of orbitals in a main energy level increases with
The value of n
Number of orbitals at each main energy level equals the
Square of the principal quantum number n^2
The electron exists in one of two possible
Spin states which creates a magnetic field
To account for the magnetic properties of the electron theoreticians created the
Spin quantum number
The spin quantum number has only two values (+1/2, -1/2) which indicate
The two fundamental spin states of an electron in an orbital
A single orbital can hold a maximum of
Two electrons but the two electrons must have opposite spin states
Number of orbitals in sublevel
2l + 1
Number of electrons possible in sublevel
[2(2l + 1)]
Total electrons possible for energy level
2n^2
