Elements, Atoms, Ions, And The Periodic Table Worksheet With Answers Page 4
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14Ne, atomic number = 10, mass = 20.18 amu
Se, atomic number = 34, mass 78.96 amu
Au, atomic number 79, mass 197.0 amu
Electron Arrangement and the Periodic Table
Bohr concluded that the energy levels of an atom can handle only a certain number of
electrons at a time.
The Quantum Mechanical Atom
J. J. Thomson had demonstrated the particle properties of the electron earlier.
Because electrons can exhibit diffraction patterns, they have a dual nature of both wave and
particle.
In 1924, Louis de Broglie suggested that the electron should have wave properties.
Light waves exhibit "diffraction."
Erwin Schrodinger developed equations to describe the regions around the nucleus where
electrons had the probability of being 95% of the time.
These regions of high probability for finding an electron around the nucleus were called
orbitals. Three dimensional models of the probability regions or orbitals can be constructed.
Electron cloud representations are used to show the space that can be occupied by electrons in
different energy levels.
Building Atoms by Orbital Filling
Schrodinger's work showed that each orbital could have a maximum of two electrons. Energy
levels could contain different numbers of orbitals. Energy levels further from the nucleus can
accommodate more orbitals than energy levels nearer the nucleus.
Energy levels can have sublevels when multiple orbitals are present.
Orbital Shapes
Picture
Sub-level
Shape
# of orbitals/energy level
s
spherical
1
p
dumbbell
3
d
complex
5
f
very complex
7
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