Periodic table period
Period 4
Period 4 is a horizontal row of the periodic table with 18 elements, from Potassium (atomic number 19) to Krypton (atomic number 36). Every element in the row has 4 occupied electron shells. Period 4 is the first long period: after potassium and calcium it opens the 3d subshell, bringing in the first row of transition metals, including iron, copper and zinc.
At a glance
- Elements
- 18
- Atomic numbers
- 19 to 36
- Blocks
- s-block, d-block, p-block
- Period
- 4
- Phase at STP
- solid (16), liquid (1), gas (1)
Shared properties
- Each member has 4 occupied electron shells
- Atomic radius generally decreases from left to right across the period
- Ionization energy and electronegativity generally increase across the period
- Character shifts from metallic on the left to nonmetallic on the right