Identify the correct statement(s) from the following.
(This question has multiple correct options)
(A) The ion having a positive charge on it is known as an electro-positive ion.
(B) The ion having a negative charge on it is known as an electro-negative ion.
(C) Simple ion is an ion which contains one or more atoms of the same element.
(D) Compound ion is an ion which contains two or more atoms of different elements forming a single unit.

Hint: (1) An ion is an atom or a group of atoms which is electrically charged. It has an unequal number of protons and electrons.
(2) An anion is a negatively charged ionic species. It has extra electrons around it. It is attracted towards the anode in electrolysis and hence the name anion. A cation is a positively charged species. It is attracted towards the cathode in electrolysis and hence the name cation.
(3) Simple monatomic ions are formed from a single atom whereas polyatomic ions are formed from a number of atoms.

Complete step by step answer: An ion which results from an atom or molecule when it loses one or more valence electrons thereby giving a positive charge is called a cation. Thus, cations have less number of electrons than protons. Since cation is a positively charged species, it is also called an electro-positive ion. So, statement A is true.
An ion which results from an atom or molecule when it gains one or more valence electrons thereby giving a negative charge is called an anion. Thus, anions have more electrons than protons. Since anion is a negatively charged species, it is also called an electro-negative ion. So, statement B is true.
There are two more categories of ions. They are simple ions and compound ions.
 Simple ions are those ions which are formed from atoms of a single element. For example, the sodium ion ${\text{N}}{{\text{a}}^{\text{ + }}}$ is a simple ion because it is formed from a single sodium atom. So, the statement C is true.
Compound ions are those ions which are formed from atoms of different elements. For example, the ammonium ion ${\text{N}}{{\text{H}}_4}^{\text{ + }}$ is a compound ion as it is formed from atoms of two different elements nitrogen and hydrogen. So, the statement D is also true.

Thus, all the four options are correct.

Note: A neutral atom has an equal number of protons and electrons and so it is neutral. The ionic radius of an ion is equal to the distance between the centre of the nucleus of the ion and its outermost shell containing electrons. When extra electrons are added, this distance will increase and hence the ionic radius of an anion will increase and will be larger than the parent atom. On the other hand, the ionic radius of a cation will be smaller than the radius of the parent atom which also means that the radius of the cation is smaller than the radius of the corresponding anion.