Question

First ionization energy

Answer 1

The first ionization energy is defined as

• Energy which is required to pull out one mole of the outermost shell's electrons in a neutral atom from one mole of gaseous atoms to produce 1 mole of gaseous ions each with a charge of 1+.
• 
  `A\to A^++ e^(-)` , where A is any neutral atom.
• In the periodic table, Its value decreases from top to bottom in groups and increases from left to right across a particular period.
• Helium has the largest first ionization energy.
• Francium has one of the lowest.