Arrangement of elements
Arranging the elements
- The Periodic Table arranges elements in order of increasing proton number.
- Rows are periods; columns are groups.
Practice
The elements in the Periodic Table are arranged in order of increasing:
The table is ordered by proton (atomic) number.
Patterns to know
- Across a period: metals (left) → non-metals (right).
- The group number gives the ion charge: Group I → $+1$, Group II → $+2$, Group VII → $-1$.
- Same group = similar chemistry, because they have the same number of outer-shell electrons.
Practice
Elements in Group I form ions with a charge of:
Group I atoms lose one electron to form +1 ions; the group number gives the charge.
Practice
Elements in the same group have similar chemistry because they have the same number of outer-shell electrons.
The outer-shell electron count, shared within a group, controls chemical behaviour.
You've got it
Key idea
- the table is ordered by proton number; periods = rows, groups = columns
- group number sets the ion charge (I → +1, VII → −1)
- same group → similar properties (same outer-shell electrons)