Question

Write note on trends of ionisation enthalpy in group and period.

Answer 1

• Trends in ionisation enthalpy in a group: The first ionisation enthalpy of elements decreases as we move down in a group. While moving down in a group, atomic number increases and the number of shells also increases. Outermost electrons are far away from the nucleus and thus can be removed easily.
  
• Trends in ionisation enthalpy across a period: As we move from left to right across a period,ionisation energy of elements increases. This is due to the decrease in size of atoms across a period. The valence electrons get closer to the nucleus of an atom as we move from left to right due to increased nuclear charge.