Elements are classified by their chemical properties, physical state, reactivity, and electron configuration. The periodic table organizes elements by these categories. Understanding classification helps predict behavior: metallic character, reactivity, bonding type, solubility, and more.
Elements: Li, Na, K, Rb, Cs, Fr
Reactivity: EXTREMELY reactive
Physical: Soft, low density, shiny
Bonding: Always +1 oxidation state
Why?: 1 valence electron, easily lost
Elements: Be, Mg, Ca, Sr, Ba, Ra
Reactivity: Very reactive
Physical: Harder than alkali metals, denser
Bonding: Always +2 oxidation state
Why?: 2 valence electrons, easily lost
Elements: Sc→Zn, Y→Cd, etc.
Reactivity: Moderate
Physical: Hard, high density, conductive
Bonding: Variable oxidation states (+2 to +7)
Why?: d electrons can be lost or shared
Elements: Al, Ga, In, Sn, Pb, Bi
Reactivity: Low to moderate
Physical: Metallic but less reactive
Bonding: Usually +3 or higher oxidation
Why?: Full d orbitals, p electrons involved
Elements: F, Cl, Br, I, At
Reactivity: EXTREMELY reactive
Physical: F, Cl gases; Br liquid; I solid
Bonding: -1 oxidation state (in compounds)
Why?: Need just 1 more electron!
Elements: He, Ne, Ar, Kr, Xe, Rn
Reactivity: INERT (essentially zero)
Physical: All gases, colorless
Bonding: Rarely form bonds
Why?: Full valence shell = perfect stability
| Category | Reactivity | Conductor? | Malleable? | Example Use |
|---|---|---|---|---|
| Alkali | Extreme | Yes | Yes | Batteries (Li) |
| Alkaline Earth | Very High | Yes | Yes | Alloys, Bones (Ca) |
| Transition | Moderate | Yes | Yes | Steel, Catalysts |
| Nonmetals | Variable | No | No | Life molecules (C, O, N) |
| Halogens | Extreme | No | No | Water treatment (Cl) |
| Noble Gases | None | No | No | Lighting, Anesthesia |