10/19/15 Electron
Configuration:
Valence
Electrons
October 1st, 2015
Valence Electrons and Writing Electron
Configuration
10/1/15
›  Objective:
write the electron configuration of an
atom and determine its valence electrons
›  Do Now:
1.  What are the sub-levels?
2.  How many orbitals are found in each sub-level?
3.  How many energy levels can an atom have?
4.  What rule states that electrons will occupy the
lowest energy orbital?
1 10/19/15 Writing Electron Configuration
›  The
“diagonal
rule” shows us the
order to place
electrons when
writing electron
configuration
Writing Electron Configuration: Practice
Atom
# Electrons
Electron Configuration
Nitrogen
Silicon
Argon
Chromium
2 10/19/15 Writing Electron Configuration: Practice
Atom
# Electrons
Electron Configuration
Nitrogen
7
1s22s22p3
Silicon
14
1s22s22p63s23p2
Argon
18
1s22s22p63s23p6
Chromium
24
1s22s22p63s23p64s23d4
Valence Electrons
The electrons in the outer most energy level (shell)
are called valence electrons
›  An atom’s valence electrons will determine its
reactivity.
›  How many valence electrons are in each atom?
› 
›  Silicon:
1s22s22p63s23p2
›  Chromium: 1s22s22p63s23p64s23d4
3