Answer:
The Standard Model of particle physics is the theory describing three of the four known fundamental forces (the electromagnetic, weak, and strong interactions, and not including the gravitational force) in the universe, as well as classifying all known elementary particles. It was developed in stages throughout the latter half of the 20th century, through the work of many scientists around the world, with the current formulation being finalized in the mid-1970s upon experimental confirmation of the existence of quarks.
Usually with roman numerals, like iron (II) chromate
iron has a charge of 2
or manganese (IV) oxide, manganese has a charge of 4
(these are ionic compounds just to let you know)
