Recall that in the periodic table, each row is called a period. The rows are aligned in such a way that the elements in each vertical column share certain characteristics. Each of these columns of the periodic table is called a group. Chemists have long found it convenient to refer to the elements of different groups, and in some cases of spans of groups, by the names shown in the table below. The two of these terms that are most important for you to know are noble gases and transition metals, but you may also notice that group family names can give clues about the elements' metallic properties (Figure 2).
When two elements are joined in a chemical bond, the element that attracts the shared electrons more strongly is more electronegative. Elements with low electronegativity are said to be electropositive and tend to have more metallic properties (Figure 1).
The fact that the metallic elements are found on the left side of the periodic table offers an important clue to the nature of how they bond together to form solids. These elements all possess low electronegativities and readily form positive ions. Because they show no tendency to form negative ions, the kind of bonding present in ionic solids can immediately be ruled out.
These points lead us to the simplest conception of metals: a lattice of positive ions immersed in a “sea of electrons” that can migrate freely throughout the solid. In effect, the electropositive nature of the metallic atoms allows their valence electrons to exist as a mobile fluid, which can be displaced by an applied electric field. This results in their high electrical conductivities. Because each ion is surrounded by the electron fluid in all directions, the bonding has no directional properties; this accounts for the high malleability and ductility of metals.