Octet Rule
Atoms form bonds in such a manner so as to have access to eight outer electrons. The outer s and p electrons of an atom are referred to as valence electrons. Recall that there
are 2 s electrons and 6 p electrons, for a total of 8 valence electrons, hence the name octet rule.
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac Rf Ha
Atoms such as helium (He), neon (Ne), argon (Ar), and krypton (Kr), which are located in the last column of the periodic table, are called Nobel Gases. They are stable, and
for many years, it was assumed that we would never make synthesize a molecule using noble gas atoms.
Atoms undergo change to gain eight valence electrons. Notice that if chlorine (Cl) loses one electron, it will have the same
number of valence electrons as argon (Ar). Also notice that if
sodium (Na) loses an electron, it will have the same number of
valence electrons as neon (Ne).
The formation of table salt (sodium chloride, NaCl) is favored
because sodium can give its "extra" electron to chlorine. When sodium loses an electron, its charge becomes +1
When chlorine gains an electron, its charge becomes -1.
Later, we will see that if two atoms both need electrons
to achieve an octet, they can share electrons with each other.
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Last Revised 02/04/98.
Copyright ©1998 by William L. Dechent. All rights reserved.