The correct answer is option 2 i.e 19.
- Potassium is a member of the alkali group of the periodic table.
- Symbol: K.
- Atomic number: 19.
- Belongs to group 1 in the periodic table.
- First isolated in 1807 by Humphry Davy.
- Sodium and Potassium are the elements known as soft metals(can cut with a knife with little force).
- Potassium metal is kept in kerosene due to its high reactivity with water.
- Potassium bicarbonate is the chemical used in fire extinguishers.
- Potassium is the most common radioisotope in the human body.
- Potassium is the second least dense metal after lithium.
- Atomic Number 17: Chlorine.
- Atomic Number 18: Argon.
- Atomic Number 20: Calcium.



