Periodic Table
The periodic table organises elements by atomic number, revealing periodic trends in properties like electronegativity and atomic radius.
The Periodic Table
The periodic table arranges elements in order of increasing atomic number, with rows (periods) and columns (groups) that reflect recurring chemical properties.
Key Trends
#### Electronegativity
Increases from left to right across a period; decreases down a group.
Most electronegative: Fluorine (3.98)
Least electronegative: Caesium (0.79)
#### Atomic Radius
Decreases from left to right (more protons pull electrons inward); increases down a group (more electron shells).
#### Ionisation Energy
Increases from left to right; decreases down a group.
Groups
| Group | Name | Valence Electrons |
|---|---|---|
| 1 | Alkali metals | 1 |
| 2 | Alkaline earth metals | 2 |
| 17 | Halogens | 7 |
| 18 | Noble gases | 8 |
Related molecules: Sodium Chloride, Oxygen
Learn more: Chemical Bonding