http://www.ck12.org Chapter 8. Ionic and Metallic Bonding
TABLE8.2:(continued)
Group Number Electron Dot Diagram
1617
18
Electron dot diagrams for all elements in a given group of representative elements are identical (except for the
elemental symbol) because each element in one of those groups has the same number of valence electrons. Most
transition metals have two valence electrons in their ground state, though some of the elements with unusual electron
configurations have only one.
Go to http://hyperphysics.phy-astr.gsu.edu/hbase/pertab/perlewis.html to answer the following question:
From this periodic table, explain how valence electrons are added to the symbol from one column to the next.The Octet Rule
The noble gases are unreactive because of their electron configurations. American chemist, Gilbert Lewis (1875-
1946), used this observation to explain the types of ions and molecules that are formed by other elements. He called
his explanation the octet rule. Theoctet rulestates that elements tend to form compounds in ways that give each
atom eight valence electrons. An exception to this rule is the elements in the first period, which are particularly
stable when they have two valence electrons. A broader statement that encompasses both the octet rule and this
exception is thatatoms react in order to achieve the same valence electron configuration as that of a noble gas.
Most noble gases have eight valence electrons, but because the first principal energy level can hold a maximum of
two electrons, the first noble gas (helium) needs only two valence electrons to fill its outermost energy level. As a
result, the nearby elements hydrogen, lithium, and beryllium tend to form stable compounds by achieving a total of
two valence electrons.
There are two ways in which atoms can satisfy the octet rule. One way is by sharing their valence electrons with
other atoms, which will be covered in the next chapter,Covalent Bonding. The second way is by transferring valence
electrons from one atom to another. Atoms of metallic elements tend to lose all of their valence electrons, which
leaves them with an octet from the next lowest principal energy level. Atoms of nonmetallic elements tend to gain
electrons in order to fill their outermost principal energy level with an octet.