First ionization energy is the amount of energy required to remove one electron from an atom in its neutral state.
First ionization energy is important because it helps us understand the reactivity and chemical properties of elements. It also determines the ease of forming positive ions and plays a crucial role in chemical bonding.
First ionization energy is measured in units of kilojoules per mole (kJ/mol). It is typically measured experimentally using various techniques such as mass spectrometry or photoelectron spectroscopy.
The factors that affect first ionization energy include the nuclear charge (number of protons), atomic radius, and the number of electrons in the outermost energy level. Generally, as the nuclear charge and number of electrons increase, the first ionization energy also increases. However, as the atomic radius increases, the first ionization energy decreases.
First ionization energy generally increases from left to right across a period in the periodic table. This is because as you move from left to right, the nuclear charge increases, making it more difficult to remove an electron. However, it decreases down a group because the atomic radius increases, making it easier to remove an electron.