Classification of Elements in the Periodic Table

Overview of Element Classifications

• Metals, non-metals, and metalloids are the three primary classifications of elements on the periodic table. Each category shares distinct physical and chemical properties that differentiate them from one another.

• The periodic table visually represents these classifications, with metalloids being limited to seven elements, while metals dominate the majority. Non-metals are primarily located on the far right side of the table.

Characteristics of Metals

Physical Properties

• Metals are typically solid at room temperature (with exceptions like mercury) and exhibit a silvery luster. They are malleable, ductile, dense, hard, and opaque. Some metals have unique colors (e.g., gold and copper).

• Certain metals can be brittle (like manganese) or soft (like sodium), which can be easily cut with a knife. Metals also conduct heat and electricity exceptionally well and form crystalline structures.

Chemical Properties

• Chemically, metals tend to lose electrons easily, forming cations during reactions due to their low ionization energies and electronegativities. This results in strong ionic bonds in compounds such as metal oxides that release OH⁻ ions in solution. For example: Na₂O + H₂O → 2NaOH.

• Oxidation numbers for metals usually range from +1 to +3 but can reach higher values (+4 for titanium and zirconium). Examples include Mn⁷⁺ and Os⁸⁺ for very positive oxidation states.

Characteristics of Non-Metals

Physical Properties

• Non-metals exist in various states; most are gases (e.g., nitrogen, oxygen), while some solids include sulfur and carbon (coal/diamond). Bromine is unique as a liquid non-metal at room temperature. Non-metals generally lack density compared to metals and appear colorless or dull but can display colors like yellow (sulfur) or purple (iodine).

Chemical Properties

• Non-metals readily gain electrons except noble gases; they form anions when combining with metal cations resulting in salts or ceramic compounds like halides or sulfides. They produce covalent compounds through shared bond electrons leading to acidic solutions upon dissolution in water (e.g., CO₂ forms H₂CO₃).

• High electronegativities characterize non-metals; fluorine is noted as the most electronegative element among them, making them effective oxidizing agents despite also having positive oxidation states under certain conditions (-F⁻ , -O²⁻ , -H⁺ ).

Characteristics of Metalloids

General Traits

• Metalloids possess mixed characteristics between metals and non-metals: they are semiconducting solids that are slightly dense yet brittle with high melting/boiling points resembling metallic appearance but behaving chemically like non-metals. Key examples include silicon, germanium, arsenic, etc.

Chemical Behavior

• Compounds formed by metalloids often exhibit amphoteric behavior reacting with both acids and bases but do not act as strong oxidizing or reducing agents themselves; their thermal conductivity varies significantly across different metalloids while electrical conductivity may resemble that of some metals like arsenic or antimony.

Unique Applications