The periodic table organizes the known chemical elements by atomic number and recurring chemical behavior. A few simple ideas—atomic number, groups, periods and blocks—make it much easier to use as an engineering reference.
Atomic number and symbol
The atomic number is the number of protons in the nucleus and uniquely identifies an element. Each element also has a one- or two-letter symbol used in formulas, specifications and technical documentation.
Groups and periods
Vertical columns are called groups. Elements in a group often share valence-electron patterns and therefore show related chemistry. Horizontal rows are periods; moving across a period reveals systematic changes in atomic size, metallic character and bonding.
The s, p, d and f blocks
The blocks reflect the type of electron orbital being filled. The s-block contains Groups 1 and 2, the d-block contains the transition metals, the p-block contains Groups 13–18, and the f-block contains the lanthanides and actinides.
Why engineers use the table
The periodic table helps explain why aluminum is lightweight, why copper conducts electricity well, why chromium improves corrosion resistance, why silicon is useful in electronics and why rare-earth elements support high-performance magnets and optical systems.
