Transcript Models of the Atom

Models of the Atom
Development of the Atomic Model
• Could Rutherford’s atomic model explain
the chemical properties of an element?
No, to describe the chemical properties of an
element we needed a model that better
describes the behavior of electrons.
The Bohr Model
• Niels Bohr (1885 – 1962) – Danish Physicist/
Student of Rutherford
– An electron is found only in specific circular paths, or
orbits, around the nucleus.
– The energy of an atom changes when it absorbs or
emits light.
– Each orbit has a fixed energy (each orbital is a
different energy level.)
– A quantum of energy is the amount of energy
required to move from one energy level to another
• The amount of energy that an electron loses or
gains in an atom is not always the same.
The energy levels in an atom are not evenly
spaced. Why do you think that is?
The further the electron is from the nucleus, the less
energy it takes to move to the next level.
The Quantum Mechanical
Model
• Erwin Schrodinger (1887-1961)
– Came up with an equation (Schrodinger equation)
that described the behavior of the electron in a
hydrogen atom.
– The quantum mechanical model (electron cloud
model):
• The modern description of electrons in an atom
• Determines the allowed energies an electron can have
and how likely it is to find the electron in various
locations around the nucleus.
• Based on probability
Atomic Orbitals
• What does solving the Schrodinger
equation show us?
-The energies an electron can have
• What do atomic orbitals show us?
-The region of space
where there is a high
probability of
finding an electron.
Atomic Orbitals (Continued)
• n : Principal quantum numbers (principal energy levels)
• n is assigned the value of (1,2,3,4,…)
• Sub levels
• For each principal energy level there are several
sublevels with different shapes that indicate where
an electron can be found
Atomic Orbitals (Continued)
• Different atomic orbitals are denoted by
different letters
– s,p,d,f
– s orbitals are spherical
– p orbitals are dumbbell shaped
– d orbitals are clover shaped (4 leaf)
– f becomes complicated to explain and you
won’t have to explain the shape.
Summary of the Principal Energy Levels , Sublevels and Orbitals
Principal energy level
Number of sublevels
Type of
sublevel
Maximum
number of
electrons
n=1
1
1s (1 orbital)
2
n=2
2
2s (1 orbital),
2p (3 orbitals)
8
n=3
3
3s (1 orbital),
3p (3 orbiatls),
3d (5 orbitals)
18
n=4
4
4s (1 orbital),
4p (3 orbitals),
4d (5 orbitals),
4f (7 orbitals)
32
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