Inorganic Chemistry (B.A./B.Sc) 1st Sem Previous Year Solved Question Paper 2022

In the second period of the periodic table, which includes elements from lithium (Li) to neon (Ne), there is a general trend in ionization enthalpy, which is the energy required to remove an electron from an atom or ion. The ionization enthalpy increases from left to right across the period. Several factors 
contribute to this variation:

1. Increasing Nuclear Charge: As you move from left to right across the second period, the number of protons in the nucleus increases. This greater positive charge in the nucleus exerts a stronger attraction on the electrons in the same energy level, making it more difficult to remove an electron. This increased nuclear charge is the primary reason for the general trend of increasing ionization enthalpy.

2. Effective Nuclear Charge: The effective nuclear charge, experienced by the valence electrons, increases due to the increasing nuclear charge. Effective nuclear charge is the net positive charge felt by the valence electrons after accounting for shielding by inner electrons. As the effective nuclear charge increases, valence electrons are held more tightly by the nucleus, requiring more energy to remove them.

3. Shielding Effect: Although there is some shielding by inner electrons, it remains relatively constant across the second period. The increase in the nuclear charge outweighs the minor effect of shielding, leading to a net increase in ionization enthalpy.

4. Energy Levels: In the second period, the number of energy levels (shells) remains the same, so the principal quantum number (n) is consistent. Since electrons in the same energy level experience similar levels of shielding, the increase in ionization enthalpy is primarily attributed to the increase in nuclear charge.

As you move from left to right across the second period, you will observe a steady increase in ionization enthalpy. This trend in ionization energy continues into higher periods of the periodic table, with exceptions and variations occurring due to electron configurations and other factors in specific elements.