An elements atomic number is 57. how many protons would an atom of this element have?

Plz choose one of the compounds from the table and explain how you know the numbers of atoms in your formula. is it possible for two different compounds to be made from the exact same two elements? why or why not? with a limited number of elements (less than 120 are known), does this mean we also have a small number of compounds or do we have a large number of compounds in this world?

If a polyatomic ionic compound has gained two hydrogen ions, then how does its name begin?

Will mark brainliest how many electrons can be held in the energy level n = 4?