Section 01
Periods and groups
Rows are called periods (energy levels of the outer electrons). Columns are called groups; elements in a group share similar chemical behavior because they have the same number of valence electrons.
Section 02
Metals, nonmetals, metalloids
Metals (left) are shiny conductors, nonmetals (upper right) are dull insulators, and metalloids (staircase) have properties of both.
Section 03
Periodic trends
Atomic radius grows down a group and shrinks across a period. Electronegativity — pulling power for electrons — does the opposite: it grows across a period toward fluorine, the most electronegative element.