> See also: > - [[Chemical Nomenclature]] > - [[Atoms and Elements]] # The Periodic Table An **element** is a [[Properties of Matter|pure substance]] that cannot be broken down into smaller substances via chemical changes. **Periodic Law:** The properties of the elements are periodic functions of their atomic numbers. - *Groups* are *vertical* columns - (18 Total) - *Periods* are *horizontal* rows - (7 Total) A modern periodic table arranges the elements in *increasing order of their atomic numbers.* ### Classifications of Elements ![[Classifications of Elements.png|700]] | Group | Location | | ----------------------- | ------------------------------------------- | | Main Group Elements | Groups: 1,2, 13-18 | | Transition Metals | Groups: 3-13 | | Inner Transition Metals | Lanthanides *(Upper)* & Actinides *(Lower)* | | Alkali Metals | Group 1 *(Exception of Hydrogen)* | | Alkaline Earth Metals | Group 2 | | Pnictogens | Group 15 | | Chalcogens | Group 16 | | Halogens | Group 17 | | Noble Gases | Group 18 | - **Metals** are shiny, malleable, good conductors of heat and electricity. - **Nonmetals** appear dull, poor conductors of heat and electricity. - **Metalloids** conduct heat and electricity moderately well and possess some properties of both metals and nonmetals ## Atomic Trends > See also: > - [[Electronegativity]] > - [[Molecular Orbital Theory]] - Size (radius of Atom) - Ionization - Electron Affinity "Only core electrons count towards **shielding**. Valence electrons..." - This, along with the gradual increase in protons causes these **periodic variations.** ### Atomic Radius ![[Pasted image 20240107173109.png|400]] **Electronegativity**