General Chemistry: Electronegativity and Ionization
Ionization Energy Overview The process of removing electrons from an atom requires increasing amounts of
energy as more electrons are removed. This is because the removal of additional electrons occurs from increasingly
positively charged species, known as cations. The first electron removed requires a specific amount of energy
termed the first ionization energy. The second electron’s removal, which occurs from a univalent cation to form a
divalent cation, requires the second ionization energy, and this pattern continues for subsequent electrons.
Example of Ionization Energies For magnesium (Mg), the equations representing the ionization process are:
1. Mg (g) → Mg* (g) + e (first ionization)
2. Mg* (g) → Mg²⁺ (g) + e (second ionization)
The respective energies required for these processes are:
First ionization energy: 738 kJ/mol
Second ionization energy: 1450 kJ/mol
Active Metals Elements in Groups IA and IIA, such as lithium and beryllium, exhibit low ionization energies,
categorizing them as active metals. These active metals do not exist in their neutral atomic forms in nature; instead,
they are typically found in ionic compounds, minerals, or ores due to their high reactivity.
Formation of Stable Electron Configurations The alkali metals (Group IA) achieve stability by losing one electron,
resulting in a filled valence shell. Similarly, alkaline earth metals (Group IIA) lose two electrons to attain a stable
configuration. This process leads to the formation of cations that resemble noble gas configurations.
Behavior of Halogens In contrast, halogens (Group VIA or Group 17) typically do not lose electrons; instead, they
tend to gain electrons to form anions. Their ionic forms are characterized by the addition of electrons rather than
the removal.
Ionization Energies The second ionization energies for Group IA monovalent cations (e.g., sodium, Na) are
significantly higher compared to those for Group IIA or subsequent monovalent cations (e.g., magnesium, Mg).
This discrepancy arises because removing a second electron from a Group IA metal disrupts a noble gas-like
configuration achieved after the first ionization.
Noble Gases and Ionization Energies Group VIIIA elements, known as noble gases or inert gases, exhibit the
highest ionization energies. They possess stable electron configurations and are highly resistant to losing electrons
due to their already filled valence shells.
Conclusion Overall, the tendency of elements to lose or gain electrons is closely linked to their group classification
in the periodic table and their pursuit of achieving stable electron configurations.
Halogens and Their Electron Affinity
Halogens are a group of elements in the periodic table known for their high reactivity, particularly due to their
tendency to gain electrons. They have seven valence electrons and require just one additional electron to complete
Ionization Energy Overview The process of removing electrons from an atom requires increasing amounts of
energy as more electrons are removed. This is because the removal of additional electrons occurs from increasingly
positively charged species, known as cations. The first electron removed requires a specific amount of energy
termed the first ionization energy. The second electron’s removal, which occurs from a univalent cation to form a
divalent cation, requires the second ionization energy, and this pattern continues for subsequent electrons.
Example of Ionization Energies For magnesium (Mg), the equations representing the ionization process are:
1. Mg (g) → Mg* (g) + e (first ionization)
2. Mg* (g) → Mg²⁺ (g) + e (second ionization)
The respective energies required for these processes are:
First ionization energy: 738 kJ/mol
Second ionization energy: 1450 kJ/mol
Active Metals Elements in Groups IA and IIA, such as lithium and beryllium, exhibit low ionization energies,
categorizing them as active metals. These active metals do not exist in their neutral atomic forms in nature; instead,
they are typically found in ionic compounds, minerals, or ores due to their high reactivity.
Formation of Stable Electron Configurations The alkali metals (Group IA) achieve stability by losing one electron,
resulting in a filled valence shell. Similarly, alkaline earth metals (Group IIA) lose two electrons to attain a stable
configuration. This process leads to the formation of cations that resemble noble gas configurations.
Behavior of Halogens In contrast, halogens (Group VIA or Group 17) typically do not lose electrons; instead, they
tend to gain electrons to form anions. Their ionic forms are characterized by the addition of electrons rather than
the removal.
Ionization Energies The second ionization energies for Group IA monovalent cations (e.g., sodium, Na) are
significantly higher compared to those for Group IIA or subsequent monovalent cations (e.g., magnesium, Mg).
This discrepancy arises because removing a second electron from a Group IA metal disrupts a noble gas-like
configuration achieved after the first ionization.
Noble Gases and Ionization Energies Group VIIIA elements, known as noble gases or inert gases, exhibit the
highest ionization energies. They possess stable electron configurations and are highly resistant to losing electrons
due to their already filled valence shells.
Conclusion Overall, the tendency of elements to lose or gain electrons is closely linked to their group classification
in the periodic table and their pursuit of achieving stable electron configurations.
Halogens and Their Electron Affinity
Halogens are a group of elements in the periodic table known for their high reactivity, particularly due to their
tendency to gain electrons. They have seven valence electrons and require just one additional electron to complete
