The odd one out is A. Iron.
The other four elements are all non-metals. Iron is a metal.
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series and is the most common element in the Earth’s crust. It is a member of the iron group in the periodic table: a group of elements in the periodic table of the chemical elements that have a similar chemical behaviour. The atomic number of iron is 26, and its atomic mass is 55.845. Iron is a solid at room temperature and has a melting point of 1538 °C and a boiling point of 2862 °C. It is a very strong metal and is used in many different applications, including construction, machinery, and transportation.
Potassium is a chemical element with the symbol K and atomic number 19. It is a soft, silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen produced. Potassium is the sixth most abundant element in the Earth’s crust and exists in nature, primarily as the mineral sylvite. Potassium is essential for life, being an important component of cell membranes and an electrolyte. It is also used in fertilizers, batteries, and explosives.
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table, and is a highly reactive element. It is an essential nutrient in all living things as a component of salt. Sodium is also used in many industrial processes, including the manufacture of glass, soap, and detergents.
Chlorine is a chemical element with the symbol Cl and atomic number 17. It is a pale yellow-green gas at standard temperature and pressure and exists as a diatomic molecule. Chlorine is an extremely reactive element and is the second most abundant halogen. It is used in many industrial processes, including the manufacture of bleach, PVC, and pharmaceuticals.
Iodine is a chemical element with the symbol I and atomic number 53. It is a non-metallic, lustrous, deep purple-black solid at standard temperature and pressure. The element has one of the highest atomic numbers of any naturally occurring non-metal. It is a member of the halogen group in the periodic table and is a highly reactive element. Iodine is used in many industrial processes, including the manufacture of pharmaceuticals, dyes, and pigments.