Excited Atoms
& Atomic Structure
, Mechanical
Picture of the Atom
Basic Postulates of Quantum Theory
1. Atoms and molecules can exist only in certain energy states. In each energy
state, the atom or molecule has a definite energy. When an atom or
molecule changes its energy state, it must emit or absorb just enough energy
to bring it to the new energy state (the quantum condition).
2. Atoms or molecules emit or absorb radiation (light) as they change their
energies. The frequency of the light emitted or absorbed is related to the
energy change by a simple equation.
hc
E h mc 2
, The Quantum Mechanical Picture of
the Atom
The allowed energy states of atoms and molecules can be described by sets of numbers called quantum numbers.
• Quantum numbers are the solutions of the Schrodinger, Heisenberg & Dirac equations.
2 ( r , t )
Schroedinger 3-dimensional 2 (r , t ) V (r , t ) (r , t ) i
time independent equation 2m t
Heisenberg’s uncertainty
Equation
Dirac’s quantum
• Four quantum numbers are necessary to describe
mechanical energy
modelstates of electrons in atoms
– n, , m, ms
E. Schrodinger W. Heisenberg
1887-1961 1901-1976
, Quantum Numbers – n
1. The Principal quantum number has the symbol – n.
n = 1, 2, 3, 4, ...... “shells”
n = K, L, M, N, ......
The electron’s energy depends principally on n and tells the average relative
distance of the electron from the nucleus.
– As n increases for a given atom, so does the average distance
of the electrons from the nucleus.
– Electrons with higher values of n are easier to remove from an
atom.
n=1
n=2
n=3
n=4
n=5
n=6
n=7
& Atomic Structure
, Mechanical
Picture of the Atom
Basic Postulates of Quantum Theory
1. Atoms and molecules can exist only in certain energy states. In each energy
state, the atom or molecule has a definite energy. When an atom or
molecule changes its energy state, it must emit or absorb just enough energy
to bring it to the new energy state (the quantum condition).
2. Atoms or molecules emit or absorb radiation (light) as they change their
energies. The frequency of the light emitted or absorbed is related to the
energy change by a simple equation.
hc
E h mc 2
, The Quantum Mechanical Picture of
the Atom
The allowed energy states of atoms and molecules can be described by sets of numbers called quantum numbers.
• Quantum numbers are the solutions of the Schrodinger, Heisenberg & Dirac equations.
2 ( r , t )
Schroedinger 3-dimensional 2 (r , t ) V (r , t ) (r , t ) i
time independent equation 2m t
Heisenberg’s uncertainty
Equation
Dirac’s quantum
• Four quantum numbers are necessary to describe
mechanical energy
modelstates of electrons in atoms
– n, , m, ms
E. Schrodinger W. Heisenberg
1887-1961 1901-1976
, Quantum Numbers – n
1. The Principal quantum number has the symbol – n.
n = 1, 2, 3, 4, ...... “shells”
n = K, L, M, N, ......
The electron’s energy depends principally on n and tells the average relative
distance of the electron from the nucleus.
– As n increases for a given atom, so does the average distance
of the electrons from the nucleus.
– Electrons with higher values of n are easier to remove from an
atom.
n=1
n=2
n=3
n=4
n=5
n=6
n=7
