Process of ionization

Ionization is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons to form ions, often in conjunction with other chemical changes. Ionization can result from the loss of an electron after collisions with subatomic particles, collisions with other atoms, molecules and ions, or through the interaction with light. Heterolytic bond cleavage and heterolytic substitution reactions can result in the formation of ion pairs. Ionization can occur through radioactive decay by the internal conversion process, in which an excited nucleus transfers its energy to one of the inner-shell electrons causing it to be ejected.

1. Process of Ionization P resenting By :- Ankkit Ghag Hritika Ghosalkar Aakanksha Ghadi Vidhit Chotaliya Sanket Muchhala Polytechnic 1 St Year EJ

2. Table Of Content Introduction Uses Production of ions Ionization energy of atoms Semi-classical description of ionization Quantum mechanical description of ionization Dissociation – distinction

3. Introduction Ionization  is the process by which an  atom  or a  molecule  acquires a negative or positive charge by gaining or losing  electrons  to form  ions , often in conjunction with other chemical changes .  Ionization can result from the loss of an electron after collisions with  subatomic particles , collisions with other atoms, molecules and ions, or through the interaction with light.  Heterolytic bond cleavage  and heterolytic   substitution reactions  can result in the formation of ion pairs. Ionization can occur through radioactive decay by the  internal conversion  process, in which an excited nucleus transfers its energy to one of the  inner-shell electrons  causing it to be ejected.

4. Uses Uses :- Everyday examples of gas ionization are such as within a  fluorescent lamp  or other  electrical discharge  lamps. It is also used in radiation detectors such as the  Geiger- Müller counter  or the  ionization chamber . The ionization process is widely used in a variety of equipment in fundamental science (e.g.,  mass spectrometry ) and in industry (e.g.,  radiation therapy ).

5. Production of ions Negatively charged ions are produced when a free electron collides with an atom and is subsequently trapped inside the electric potential barrier, releasing any excess energy. The process is known as  electron capture ionization . Positively charged ions are produced by transferring a sufficient amount of energy to a bound electron in a collision with charged particles (e.g. ions, electrons or positrons) or with photons. The threshold amount of the required energy is known as  ionization potential . The study of such collisions is of fundamental importance with regard to the few-body problem (see article on  few-body systems ), which is one of the major unsolved problems in physics.

6. Ionization energy of atoms The trend in the  ionization energy  of atoms is often used to demonstrate the periodic behavior of atoms with respect to the atomic number, as summarized by ordering atoms in  Mendeleev's table . This is a valuable tool for establishing and understanding the ordering of electrons in  atomic orbitals  without going into the details of wave functions or the ionization process.

7. Semi-classical description of ionization Classical physics  and the  Bohr model  of the atom can qualitatively explain  photoionization  and collision-mediated ionization. In these cases, during the ionization process, the energy of the electron exceeds the energy difference of the potential barrier it is trying to pass. The semi-classical description, however, cannot describe  tunnel ionization  since the process involves the passage of electron through a classically forbidden potential barrier.

8. Quantum mechanical description of ionization The interaction of atoms and molecules with sufficiently strong laser pulses leads to the ionization to singly or multiply charged ions. The ionization rate, i.e. the ionization probability in unit time, can only be calculated using  quantum mechanics . In general, the analytic solutions are not available, and the approximations required for manageable numerical calculations do not provide accurate enough results. However, when the laser intensity is sufficiently high, the detailed structure of the atom or molecule can be ignored and analytic solution for the ionization rate is possible.

9. Dissociation – distinction A substance may  dissociate  without necessarily producing ions. As an example, the molecules of table sugar dissociate in water (sugar is dissolved) but exist as intact neutral entities. Another subtle event is the dissociation of  sodium chloride  (table salt) into sodium and chlorine ions. Although it may seem as a case of ionization, in reality the ions already exist within the crystal lattice. When salt is dissociated, its constituent ions are simply surrounded by water molecules and their effects are visible (e.g. the solution becomes  electrolytic ). However, no transfer or displacement of electrons occurs. Actually, the chemical synthesis of salt involves ionization. This is a chemical reaction.

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