Electrons and Electron
Arrangement.
General info on electrons
• Electrons have a negative charge
• A neutral atom has the same number of
electrons as protons.
• The mass of an electron is extremely
small. Approximately 2000 electrons = the
mass of one proton.
• The electrons determine the size of the
atom. The nucleus determines the mass of
the atom.
•
Electrons spin around the nucleus in
pairs in orbitals. These orbitals make
up the electron cloud.
General info on electrons
continued
► The
definition of an orbital: A 3 dimensional
space with a high probability of finding a
pair of electrons.
► The 2 electrons which make a pair, spin in
opposite direction from each other in the
orbital.
►
Electron arrangements
(configurations)
 The electrons of any atom are very well
organized. The first level of organization is
the energy levels.
 Every atom’s electron cloud consists of 7
energy levels or shells.
 Each energy level (e.l.) has a specific
energy requirement. For example,
electrons in the first e.l. have less energy
than electrons in the second e.l.
 Although all atoms have 7 energy levels,
these levels may not be completely filled
with electrons or have any electrons at all.
Energy levels

Each energy level has a maximum amount of
electrons that it will contain.
Level one: holds 2 electrons
 Level two: 8 electrons
 Level 3: 18 electrons
 Level 4: 32 electrons
 Levels 5-7: 32 electrons

Diagram of the energy
levels for an element
Examples of energy levels with
electrons for some elements
Orbitals within energy levels
• With in each e.l. there
is further organization.
There are specific
orbitals.( remember an
orbital contains a pair
of electrons.)
• The e.l.s and their
orbitals with electrons
are arranged as
follows:

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E.L.
1
2
3
4
Orbitals
total
electrons
s = 2 e2
s=2 e-, p=6 e8
s=2 e-, p=6e-, d=10e18
s=2e-, p=6e-, d=10e-, f=14e- 32
Shapes of the orbitals
Orbital shapes cont.
Shapes of orbitals
Continuous Spectrum
Electrons produce light



Electrons are capable of producing light when
energy is supplied.
The electrons receive energy and are able to
leave their ground state energy level and move
to higher energy levels.
At the higher energy level, the electrons are
unstable and so return to their original ground
state releasing the energy absorbed in the form
of light.
Electrons produce light continued.



This energy emitted corresponds to a particular
wavelength and shows up as a line in the
spectrum.
When electrons return to the first level (n=1)
the series of lines occurs in the ultraviolet region
as this involves the largest energy change.
When electrons drop to other levels different
waves lengths of light are produced in the
visible light range.
Emission spectrum of hydrogen
Hydrogen spectrum
Emission lines
Each spectrum is unique for each
element



Since every element has a unique valence
electron arrangement, every element has a
unique spectrum.
The energy released when an electron drops
from one energy level to another is unique to
each element, thus, giving a unique spectrum.
The spectrum for a given element can be used to
identify the element such as a fingerprint can
identify a human.
Emission Spectra of some elements
Continuous, absorption,emission