Trends in Ionization Energy:

Here's a concise explanation of the ionization energy trends and ion formation:

• Trends in Ionization Energy:

  • Across a Period (e.g., Li to Be): Ionization energy generally increases. For example, the first ionization energy ($I_1$) of Li is 520.2 kJ/mol, while for Be it is 899.5 kJ/mol. This is because increasing nuclear charge pulls valence electrons more strongly.
  • Down a Group: Ionization energy generally decreases. This is due to increased atomic radius and greater shielding by inner electrons, making valence electrons easier to remove. (The provided table does not contain data to illustrate this trend directly).

• Alkali Metals (e.g., Lithium, Li): Lithium (electron configuration $1s^2 2s^1$) readily loses its single $2s^1$ valence electron ($I_1 = 520.2$ kJ/mol) to form a stable $\text{Li}^+$ ion with a noble gas configuration ($1s^2$). The second ionization energy ($I_2 = 7298.2$ kJ/mol) is significantly higher (about 14 times $I_1$) because it involves removing an electron from a stable, full inner shell. This large energy jump explains why alkali metals form +1 ions but not +2 or +3 ions.

• Alkaline Earth Metals (e.g., Beryllium, Be): Beryllium (electron configuration $1s^2 2s^2$) readily loses both its $2s^2$ valence electrons ($I_1 = 899.5$ kJ/mol, $I_2 = 1757.1$ kJ/mol) to form a stable $\text{Be}^{2+}$ ion with a noble gas configuration ($1s^2$). The third ionization energy ($I_3 = 14848.8$ kJ/mol) is significantly higher (about 8.5 times $I_2$) because it involves removing an electron from a stable, full inner shell. This large energy jump explains why alkaline earth metals form +2 ions but not +3 or +4 ions.