distinguish between positive ion and negative ion based on its movement on passing current
Answers
In the simplest sense, an atom consists of a nucleus containing positively charged protons and neutrons which have no net charge. The nucleus is also surrounded by electrons which have the same magnitude of charge as a proton but are negatively charged. Atoms have no net charge and so have the same number of electrons as protons.
However if an electron is removed from the atom via a process such as ionisation or beta minus decay then the number of protons will be one greater than the number of electrons. This will cause the atom to now have a relative charge of 1+. The resulting particle will be known as an ion. If further electrons are lost then the resulting ion will have a charge of +2, +3 and so on. The total relative charge of the ion is equal to the total number of electrons removed from the atom. This is equal to the number of protons minus the number of electrons.
Electrons can also be added to an atom in a process called electron affinity. If electrons are added to an atom then the atom will have a net negative charge and will become a negatively charged ion. If 1 electron is added the ion will have a relative charge of -1.