Potassium fits all your specifications and it is very important for plant growth.
It affects a plant's tolerance to hot and cold weather, drought and pests, as well as acting as a catalyst for several processes necassary to keep a plant alive and growing.
Magnesium is the soft reactive low density metallic element that is important for healthy plant growth. It is a crucial component of chlorophyll, which is responsible for photosynthesis in plants. Magnesium also plays a role in enzyme activation, cell membrane stability, and nutrient transportation within plants.
You can't compare the two in that sense. Sulphate is an ion and iron is a metallic element.
Potassium (K) is an element. It is available on the periodic table of elements.
potassium is a soft silver white highly or explosively reactive metallic element that occurs in nature only compounds.
Fluorine is the most chemically reactive non-metallic element. (Fluorine is the most reactive of all the elements, actually.) It is known as the hungry wolf of the periodic table - and it earned that nickname.
Francium (Fr) should, based on its position in the periodic table, be the most reactive metallic element. However, fluorine is the most reactive element generally.
Hydrogen
Calcium is an element, silvery metallic, soft, and reactive.
It should be noted that francium is not the most reactive element, but is the most reactive metallic element. Francium has the lowest electronegativity and the greatest electropositivity; the chemistry of francium is practically unknown today.
The element copper makes the blue-green fireworks.
Gold.
You can't compare the two in that sense. Sulphate is an ion and iron is a metallic element.
All metals are highly reactive because of their properties. As you move left on a period while moving down you move close to Francium (most-metallic). Since group 1 is the most farthest left group, it is the most metallic, therefore the most reactive.
Potassium (K) is an element. It is available on the periodic table of elements.
potassium is a soft silver white highly or explosively reactive metallic element that occurs in nature only compounds.
Osmium (Os) is the metallic element with the highest density at 22.61 g/cm3.
Fluorine is the most chemically reactive non-metallic element. (Fluorine is the most reactive of all the elements, actually.) It is known as the hungry wolf of the periodic table - and it earned that nickname.
Francium (Fr) should, based on its position in the periodic table, be the most reactive metallic element. However, fluorine is the most reactive element generally.