Periodic Law & Chemical Element Classification System
The Periodic Table of Elements organizes all known chemical elements in order of atomic number (proton count in the nucleus), demonstrating the 'Periodic Law' where chemical and physical properties recur periodically. Created by Dmitri Mendeleev in 1869 with 63 known elements, modern quantum mechanics and electron orbital theory have formally completed the table from Hydrogen (H, 1) to Oganesson (Og, 118).
The Toolbase Periodic Table Dictionary provides rapid lookups for exact standard atomic weights (u), phase at room temperature (solid, liquid, gas), density, melting points, boiling points, condensed electron configuration notation, and historical applications with a single click.
Complete 118 Chemical Elements Database
Comprehensive physical and chemical measurement data for all 118 elements according to IUPAC standards from Hydrogen (#1) to Oganesson (#118).
Real-Time Multi-Field Search & Highlighting
Instantly filters and highlights matching elements on the grid as you type by element name, symbol, or atomic number.
10 Chemical Category Color Palettes
Color-coded classifications covering alkali metals, alkaline earths, transition metals, halogens, and noble gases with hover filter interactions.
1. The 10 Periodic Table Chemical Categories Specification Table
Key characteristics, orbital fills, and standard states across element series.
| Chemical Category | Key Element Examples | Valence Electrons & Chemistry | State at 25°C / 1 atm |
|---|---|---|---|
| Reactive Nonmetals | Hydrogen (H), Carbon (C), Oxygen (O), Nitrogen (N) | High electronegativity, forms anions and covalent bonds | Gas / Solid |
| Noble Gases | Helium (He), Neon (Ne), Argon (Ar), Xenon (Xe) | Complete valence octet, chemically inert | Colorless, odorless gas |
| Alkali Metals | Lithium (Li), Sodium (Na), Potassium (K), Cesium (Cs) | Single valence electron (s1), soft and violently reactive with water | Reactive solid |
| Alkaline Earth Metals | Beryllium (Be), Magnesium (Mg), Calcium (Ca) | Two valence electrons (s2), shiny and moderately reactive | Hard solid |
| Metalloids | Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As) | Intermediate properties, crucial for semiconductors | Solid |
| Halogens | Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I) | 7 valence electrons (p5), highly reactive oxidizers | Gas / Liquid / Solid |
| Transition Metals | Iron (Fe), Copper (Cu), Gold (Au), Silver (Ag), Titanium (Ti) | Involves d-orbitals, forms colored complex ions | Solid (Mercury is liquid) |
| Lanthanides | Lanthanum (La), Neodymium (Nd), Europium (Eu) | Fills 4f-orbitals, strong magnetic and phosphorescent traits (Rare Earths) | Solid |
| Actinides | Uranium (U), Plutonium (Pu), Thorium (Th) | Fills 5f-orbitals, all radioactive heavy nuclear fuels | Radioactive solid |
| Post-Transition Metals | Aluminum (Al), Gallium (Ga), Tin (Sn), Lead (Pb) | Softer metals with lower melting points in p-block | Solid |
2. Electron Configuration Notation Guide
Horizontal rows (Periods) correspond to the principal quantum number ($n=1, 2, 3...$), while vertical columns (Groups) reflect the number of valence electrons.
Electrons fill orbitals in order of increasing energy levels according to the Aufbau principle ($1s \to 2s \to 2p \to 3s \to 3p \to 4s \to 3d...$).
Condensed Noble Gas Notation: For Iron (#26), "[Ar] 3d6 4s2" denotes the core Argon (#18) configuration with 6 electrons in the 3d orbital and 2 in the 4s orbital.
3. Room Temperature States & Radioactive Isotope Mass Numbers
① Only two elements exist naturally as liquids at standard room temperature (25°C, 1 atm): Mercury (Hg, #80) and Bromine (Br, #35).
② For synthetic transuranic radioactive elements with no stable isotopes (e.g. Neptunium #93 to Oganesson #118), mass numbers are noted in parentheses like (294), representing the isotope with the longest half-life.
Frequently Asked Questions (FAQ)
Q.Which elements are liquids at standard room temperature (25°C)?
Across all 118 elements, only two exist as liquids at 25°C and 1 atm: Mercury (Hg, #80, metal) and Bromine (Br, #35, nonmetal).
Q.Are synthetic radioactive elements included in the dictionary?
Yes. All synthetic transuranic elements from Technetium (#43) and Neptunium (#93) through Oganesson (#118) are fully documented.
Q.Why are some atomic masses enclosed in parentheses like (294)?
Elements lacking stable isotopes have their longest-lived known isotope mass number enclosed in parentheses under IUPAC standards.
Q.What fields can I search in the search bar?
You can search by English name (Hydrogen), element symbol (H, Fe), or atomic number (1, 26) to highlight matching elements in real-time.
Q.Where are Rare Earth Elements located in the periodic table?
Rare Earth elements comprise the 15 Lanthanides (atomic numbers 57 to 71 in Period 6) along with Scandium (Sc, #21) and Yttrium (Y, #39).
Q.Is my search data sent to any remote server?
No. The entire 118-element database and search filter run client-side in your browser memory.