Electron Arrangements
Lewis Dot Structures
Electron Arrangements
Learning Objectives
• Express the arrangement of electrons in atoms using
Lewis valence electron dot structures
Lewis Dot Structures
• Valence electron – an electron in an atom’s highest
occupied energy level
– Outermost electrons of the electron cloud
– Establish chemical characteristics of elements
– Only electrons shown in Lewis electron dot structures
• Symbolized as dots
Lewis Dot Structures
• Number of valence electrons is the same as the group
number for representative elements
Lewis Dot Structures
• Helium is an exception because its highest occupied
energy level can only hold two electrons
Lewis Dot Structures
• Number of valence electrons determines behavior
– Elements in the same group have similar chemical properties
Drawing an Electron Dot Structure
Step 1
Identify the symbol for the element and its number of
valence electrons using the periodic table.
Step 2
Place the corresponding number of electron dots
around the symbol. Imagine that the symbol has four
sides: top, right, bottom, and left. Begin by assigning
one dot per side, moving clockwise around the symbol.
Then, if there are still more dots to assign, start adding a
second dot to each side until all of the valence electrons
have been accounted for.
Drawing an Electron Dot Structure
Ex) Draw the electron dot structure for phosphorus.
Step 1
Identify the symbol for the element and its number of valence
electrons using the periodic table.
The symbol for phosphorus is P. Phosphorus is in group 5A so it
has 5 valence electrons.
Step 2
Place the corresponding number of electron dots around the
symbol. Imagine that the symbol has four sides: top, right, bottom,
and left. Begin by assigning one dot per side, moving clockwise
around the symbol. Then, if there are still more dots to assign, start
adding a second dot to each side until all of the valence electrons
have been accounted for.
Does the result make sense? Yes.
Electron Arrangements
Learning Objectives
• Express the arrangement of electrons in atoms using
Lewis valence electron dot structures