Periodic Table Guide — Element Categories, Trends, and Properties
The periodic table organises all 118 known elements by atomic number and chemical behaviour. The interactive periodic table on PublicSoftTools lets you explore every element, filter by category, and see atomic mass at a glance — without memorising a poster.
Element Category Reference
| Category | Key examples | Key properties |
|---|---|---|
| Alkali Metals | Li, Na, K, Rb, Cs | Highly reactive, soft, lose 1 electron, react violently with water |
| Alkaline Earth Metals | Be, Mg, Ca, Sr, Ba | Reactive, lose 2 electrons, form basic oxides |
| Transition Metals | Fe, Cu, Ni, Au, Ag | Variable oxidation states, form coloured compounds, good conductors |
| Noble Gases | He, Ne, Ar, Kr, Xe | Full outer shells, inert, used in lighting and welding |
| Halogens | F, Cl, Br, I | Reactive nonmetals, gain 1 electron, form salts with metals |
| Lanthanides | La to Lu (57–71) | f-block metals, used in magnets, lasers, and phosphors |
How to Use the Periodic Table
- Open the interactive periodic table.
- Click any element to see its atomic number, symbol, name, atomic mass, and category.
- Use the Highlight filter buttons above the table to isolate element categories.
- Hover over elements for the full name as a tooltip.
- The lanthanides and actinides appear in the separate f-block rows below the main table.
Periodic Trends
Atomic radius
Atomic radius increases going down a group (more electron shells added) and decreases going left to right across a period (more protons pull electrons closer). Caesium (Cs, Z=55) has the largest atomic radius of stable elements; fluorine (F, Z=9) has the smallest among nonmetals.
Electronegativity
Electronegativity measures how strongly an atom attracts electrons in a bond. It increases left to right across a period and decreases going down a group. Fluorine is the most electronegative element (Pauling scale: 3.98). Noble gases are excluded as they do not typically form bonds.
Ionisation energy
First ionisation energy is the energy required to remove the outermost electron. It increases left to right across a period (outer electrons are held more tightly as nuclear charge increases) and decreases going down a group (outer electrons are further from the nucleus). Noble gases have the highest ionisation energies in each period.
Key Groups to Memorise
Group 1 — Alkali Metals
Li, Na, K, Rb, Cs, Fr. All have one valence electron and react vigorously with water to form hydroxides and hydrogen gas. Reactivity increases down the group — francium is the most reactive metal, but it is radioactive and extremely rare.
Group 17 — Halogens
F, Cl, Br, I, At. All have seven valence electrons and readily gain one electron to form −1 ions. Reactivity decreases down the group — fluorine is the most reactive element in the table. Halogens form salts (halides) when reacting with metals.
Group 18 — Noble Gases
He, Ne, Ar, Kr, Xe, Rn, Og. Full outer shells make them chemically inert under standard conditions. He has 2 valence electrons; all others have 8. Used in lighting (neon signs), welding (argon), balloons (helium), and as inert atmospheres.
Symbols from Latin Names
Several common elements have symbols derived from their Latin names — a frequent source of exam errors:
- Fe — Iron (Ferrum)
- Cu — Copper (Cuprum)
- Ag — Silver (Argentum)
- Au — Gold (Aurum)
- Hg — Mercury (Hydrargyrum)
- Pb — Lead (Plumbum)
- Sn — Tin (Stannum)
- Na — Sodium (Natrium)
- K — Potassium (Kalium)
Explore the Periodic Table
Click any element for properties, filter by category, and study periodic trends interactively.
Open Periodic Table