Periodic table
- arranged in order of ascending/ increasing atomic numbers
- horizontal = periods
- verticals = groups
- two number against:
Electron arrangement of atoms
|
Electrons max. |
| Outermost shell |
18, (8 for first 20) |
| Second shell |
8 |
| Innermost shell |
2 |
Electron configurations and Periodic Table
- Groups
- vertical columns
- = no. of outermost shell electrons
- Group I: alkali metals
- Group II: alkaline earth metals (found in rocks in earth crust)
- Group VII: halogens (-ine)
- Group VIII: noble gases (not reactive)
<aside>
🗣 Hydrogen does not belongs to any groups
- non-metal, doesn’t have same properties as Group I which are all metals
</aside>
- Periods
- horizontal rows
- = no. of occupied electron shells
<aside>
🗣 Elements near the zig-zag line are semi-metals/ metalloid
</aside>
Chemical properties of elements in the same group
- depends on no. of electrons