Chemistry: The Periodic Table Overview

Study Notes

The periodic table of elements is a chart displaying chemical elements, organized by atomic number, electron configuration, and recurring chemical properties, showing periodic trends.
The table has 7 rows (periods), with metals on the left and nonmetals on the right.
The atomic number represents the number of protons in an atom of the element.
The atomic symbol is an abbreviation for the element.
The atomic weight is the average mass of the element in atomic mass units (amu).

Alkali metals are the most reactive metals, having a single loosely bound valence electron. They exhibit low ionization energy and electronegativity.
Alkaline earth metals have two valence electrons, readily forming divalent cations. They are also known for their low electron affinity and electronegativity.
Transition metals include lanthanides, actinides, and basic metals. These elements are typically hard, shiny, ductile, malleable, and conduct heat and electricity well. Transition metals can form cations with multiple oxidation states.
Metalloids (Semimetals) have properties between metals and nonmetals, and often function as semiconductors. Their reactivity depends on the elements involved in the reaction.
Nonmetals have high ionization energy, electronegativity, and are poor conductors of heat and electricity. They often form brittle solids.
Halogens have high electronegativity and are very reactive, typically exhibiting a -1 oxidation state.
Noble Gases have complete valence electron shells, which makes them unreactive and have very low electronegativity or electron affinity.

Valence, also known as oxidation state, reflects the number of electrons an atom will accept (negative number) or donate (positive number) to form a chemical bond.