Electron Cloud Model of the Atom

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Electron Cloud Model of the Atom
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What is an orbital????

• An orbital is a 3 dimensional area in space where
  an electron may be found. It does not have a set
  pattern to it like in the Bohr Model of the atom!
• It is a cloud like area around the nucleus where
  the electron can be found 95 of the time. Much
  like light, electrons have properties of both a
  particle and a wave and do not travel in a path
  like planets around a star!!!!

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The Heisenberg Uncertainty Principle

• This states that it is impossible to know both
  the position and velocity of an electron at the
  same time.
• So in an orbital (electron cloud) it is not
  possible to know exactly where an electron is at
  any one moment. The orbital represents an area
  in space , the probability of finding electrons
  in that region.

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• This model is also sometimes called the quantum
  mechanical model of the atom

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Quantum numbers

• There are 4 different quantum numbers.
• These quantum numbers describe the location of an
  electron around the nucleus of the atom
• No 2 electrons can have the same 4 quantum
  numbers in an atom. If they did it would
  indicate that they are occupying the same area in
  space around the nucleus

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Principal Quantum Number

• Generally symbolized by n, it denotes the energy
  level in which the electron is located.
• These are whole numbers, 1,2,3,.

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Angular Momentum Quantum Number

• The angular momentum quantum number, denotes the
  orbital in which the electron is located. This
  indicates the shape of the orbital

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The four types of orbitals

• The 4 types of orbitals are called
• s, p, d and f
• s orbitals are spherical in shape

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p orbitals have a figure 8 type shape there
are 3 kinds of p orbitals
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d orbitals are mostly like a 4 leaf clover type
shape. There are 5 kinds of d orbitals
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f orbital shapes become more complex. There are
7 kinds of f orbitals
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Magnetic Quantum Number

• The magnetic quantum number shows the orientation
  of the electrons orbital with respect to the
  three axes in space.

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Spin Quantum Number

• Spin quantum number denotes the behavior
  (direction of spin) of an electron within a
  magnetic field.
• Possibilities for electron spin
• 1/2 or 1/2

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4.3 Electron Configuration

• 3 rules for adding electrons to orbitals
• Aufbau principle an electron occupies the
  lowest-energy orbital that can receive it
• Pauli exclusion principle no two electrons in
  the same atom can have the same set of four
  quantum numbers
• Hunds rule orbitals of equal energy are each
  occupied by one electron before any orbital is
  occupied by a second electron, and all electrons
  in singly occupied orbital must have the same
  spin

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Representing electron configuration

• The electron configuration for boron is 1s22s22p1
• How many electrons are present in an atom of
  boron?
• What is the atomic number?
• Write the orbital notation for boron
• ?? ?? ? ___ ___
• 1s 2s 2px 2py 2pz

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Practice write the electron configuration for
nitrogen

• ?? ?? ? ? ?
• 1s 2s 2px 2py 2pz

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Maximum number of electrons in each sublevel

• s orbital 2 electrons
• p orbital 6 electrons
• d orbital 10 electrons
• f orbital 14 electrons

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Orbital filling table
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• Electron configuration of the elements of the
  first three series

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Irregular confirmations of Cr and Cu
Chromium steals a 4s electron to half fill its
3d sublevel
Copper steals a 4s electron to FILL its 3d
sublevel