The elements are draggable. Use your mouse/finger to move them. To mix these, simply put them in the blender and then click/tap the stage. Keep in mind that the blender reacts to what you put in there! Also you can't put 2 chlorines in there and you can't put Hydrogen and Sodium in there. Anything else will have the blender mix it!
Blender by Jacknjellify. (no scratch account)