There's no rule used to identify a monoatomic, anion, cation, binary acid, oxalic acid and ionic compounds.
However, we can say they all have general characteristics.
A monoatomic element refers to a single "stand-alone" element. An example of this would be group 8 elements.
Anion
An anion is a negatively charge molecule, atom or particle in a given reaction. When two charges i.e cation and anion of equal charge combine together, they neutralize the charges to form a neutrally charged compound or molecule. An example of this is Cl⁻
Cation
A cation is a positively charge molecule or atom in a given reaction.
Cations just liek anions combine togther to give a nuetrally charged molecule. An example of this is Na⁺.
Binary Acid
A binary acid are molecular compounds in which hydrogen atoms are combined with a second non-metallic element. They usually have a general formula of H-X where X stands for a non-metallic element. An example of this is HBr, HCl etc.
Oxyacids
Oxyacids are acids that contain oxygen atom. The name "oxyacid" is coined from the word "oxygen" i.e it has oxygen atom contained in it. This is sometimes the product of an acid reacting with water. An example of this is HClO⁻₄.
Ionic Compounds
Ionic compounds are also known as electrovalent compounds which are formed when two elements come together with exchange of electrons to form a new bond. This is usually a strong bond and it is formed by two type of ions which are the cations and anions. An example of this is NaCl, Na₂SO₄.