Ionization Energy

Definition:

Ionization energy is the amount of energy required to remove an electron from a neutral atom or ion in its gaseous state. It is a measure of how tightly an atom holds onto its electrons. The energy required to remove the first electron is called the first ionization energy, the second electron requires the second ionization energy, and so on.

       OR

Ionization energy is the minimum amount of energy required to remove an electron from an isolated, gaseous atom or ion.

In simpler terms:

Imagine an atom as a tiny solar system, with the nucleus as the sun and electrons orbiting around it. Ionization energy is the amount of energy you need to “pull” one of those electrons away from the nucleus and completely remove it from the atom.  

Factors Affecting Ionization Energy:

• Nuclear Charge: A higher nuclear charge (more protons in the nucleus) attracts electrons more strongly, making it harder to remove them. Therefore, ionization energy generally increases across a period in the periodic table.   
• Atomic Radius: As the atomic radius increases, the distance between the nucleus and the outermost electrons increases. This weakens the electrostatic attraction between the nucleus and the electrons, making it easier to remove them. Therefore, ionization energy generally decreases down a group in the periodic table.

• Electron Shielding: Inner electrons shield outer electrons from the full attractive force of the nucleus. This shielding effect reduces the effective nuclear charge experienced by the outermost electrons, making them easier to remove