General Chemistry: Electronegativity and Ionization
The Chemistry of Groups
Alkali Metals (IA)
The alkali metals, found in Group IA or Group 1 of the periodic table, exhibit several distinctive physical and
chemical properties. These metals are characterized by their low densities compared to other metals. Each alkali
metal has a single loosely bound electron in its outermost shell, which significantly influences their chemical
behavior. The effective nuclear charge (Z_eff) for these elements is very low, resulting in the largest atomic radii
within their respective periods.
This low Z_eff also accounts for several important trends among alkali metals:
Ionization Energies: They have low ionization energies, making it easy for them to lose their outermost
electron.
Electron Affinities: Their electron affinities are also low, indicating a weak tendency to gain electrons.
Electronegativity: Alkali metals possess low electronegativities, meaning they do not attract electrons strongly.
Due to these properties, alkali metals readily form univalent cations by losing one electron. They react vigorously
with nonmetals, particularly halogens, leading to the formation of ionic compounds such as sodium chloride
(NaCl). Additionally, when exposed to water, alkali metals react violently to produce strong bases and hydrogen gas.
ALKALINE EARTH METALS (IA)
-Group IIA or Group 2 elements.
-Characteristic properties of metals.
-Slightly higher effective nuclear charges than alkali metals.
-Smaller atomic radii compared to alkali metals.
-Two valence electrons, easily removed to form divalent cations.
-Known as active metals due to high reactivity; not found in elemental state.
CHALCOGENS (VIA)
-Group VIA or Group 16 elements.
-Composed of nonmetals and metalloids.
-Less reactive than halogens but essential for biological functions.
-Six valence electrons in their outer shell.
-Small atomic radii and large ionic radii due to proximity to metalloids.
Halogens (Group VIIA)
High Reactivity: Halogens exhibit uniform chemical reactivity, primarily due to their high electron negativities
and electron affinities.
Elemental State: They are not found in nature as free elements; instead, they exist as ions (halides) or diatomic
molecules (e.g., Cl2, F2).
, Fluorine’s Electronegativity: Fluorine is the most electronegative element, making it particularly reactive with
alkali and alkaline earth metals.
Noble Gases (Group VIIIA)
Inertness: Noble gases are characterized by minimal chemical reactivity owing to their filled valence shells.
Ionization Energies: They possess high ionization energies and show little to no tendency to gain or lose
electrons. For helium (He), neon (Ne), and argon (Ar), electronegativities are negligible.
Physical Properties: These gases have extremely low boiling points and remain gaseous at room temperature.
Commercial Use: Their lack of reactivity makes noble gases suitable for applications such as lighting sources.
Oxygen and Its Importance
Oxygen is a crucial element, being a primary component of water, carbohydrates, and various biological
molecules.
It plays a vital role in sustaining life and is essential for respiration in aerobic organisms.
Sulfur is significant for the structure of certain amino acids and vitamins, contributing to protein synthesis and
metabolic functions. Selenium serves as an important nutrient for microorganisms and aids in protecting cells from
oxidative stress, highlighting its role in maintaining cellular health. Many elements within this group are metallic and
can be toxic to living organisms at high concentrations, despite their biological usefulness.
Halogens (Group VIIA) Characteristics
Halogens are highly reactive nonmetals with seven valence electrons, seeking to complete their octets by
gaining an additional electron.
Their physical states vary under standard conditions: gaseous (Fluorine and Chlorine), liquid (Bromine), and
solid (Iodine).
Conclusion on Elemental Toxicity
It is critical to recognize that while many elements have beneficial roles in biology, they can become toxic or
damaging at elevated concentrations.
Points of Transition Metals
1. General Characteristics:
Transition metals are located in Groups IB to VIIIB (Groups 3 to 12) of the periodic table.
They are classified as metals with distinct physical and chemical properties.
2. Electron Properties:
Low electron affinities, low ionization energies, and low electronegativities characterize these elements.
The presence of loosely held electrons contributes to their metallic properties.
3. Physical Properties:
Transition metals are known for their hardness and high melting and boiling points.
They exhibit malleability, allowing them to be shaped without breaking.
The Chemistry of Groups
Alkali Metals (IA)
The alkali metals, found in Group IA or Group 1 of the periodic table, exhibit several distinctive physical and
chemical properties. These metals are characterized by their low densities compared to other metals. Each alkali
metal has a single loosely bound electron in its outermost shell, which significantly influences their chemical
behavior. The effective nuclear charge (Z_eff) for these elements is very low, resulting in the largest atomic radii
within their respective periods.
This low Z_eff also accounts for several important trends among alkali metals:
Ionization Energies: They have low ionization energies, making it easy for them to lose their outermost
electron.
Electron Affinities: Their electron affinities are also low, indicating a weak tendency to gain electrons.
Electronegativity: Alkali metals possess low electronegativities, meaning they do not attract electrons strongly.
Due to these properties, alkali metals readily form univalent cations by losing one electron. They react vigorously
with nonmetals, particularly halogens, leading to the formation of ionic compounds such as sodium chloride
(NaCl). Additionally, when exposed to water, alkali metals react violently to produce strong bases and hydrogen gas.
ALKALINE EARTH METALS (IA)
-Group IIA or Group 2 elements.
-Characteristic properties of metals.
-Slightly higher effective nuclear charges than alkali metals.
-Smaller atomic radii compared to alkali metals.
-Two valence electrons, easily removed to form divalent cations.
-Known as active metals due to high reactivity; not found in elemental state.
CHALCOGENS (VIA)
-Group VIA or Group 16 elements.
-Composed of nonmetals and metalloids.
-Less reactive than halogens but essential for biological functions.
-Six valence electrons in their outer shell.
-Small atomic radii and large ionic radii due to proximity to metalloids.
Halogens (Group VIIA)
High Reactivity: Halogens exhibit uniform chemical reactivity, primarily due to their high electron negativities
and electron affinities.
Elemental State: They are not found in nature as free elements; instead, they exist as ions (halides) or diatomic
molecules (e.g., Cl2, F2).
, Fluorine’s Electronegativity: Fluorine is the most electronegative element, making it particularly reactive with
alkali and alkaline earth metals.
Noble Gases (Group VIIIA)
Inertness: Noble gases are characterized by minimal chemical reactivity owing to their filled valence shells.
Ionization Energies: They possess high ionization energies and show little to no tendency to gain or lose
electrons. For helium (He), neon (Ne), and argon (Ar), electronegativities are negligible.
Physical Properties: These gases have extremely low boiling points and remain gaseous at room temperature.
Commercial Use: Their lack of reactivity makes noble gases suitable for applications such as lighting sources.
Oxygen and Its Importance
Oxygen is a crucial element, being a primary component of water, carbohydrates, and various biological
molecules.
It plays a vital role in sustaining life and is essential for respiration in aerobic organisms.
Sulfur is significant for the structure of certain amino acids and vitamins, contributing to protein synthesis and
metabolic functions. Selenium serves as an important nutrient for microorganisms and aids in protecting cells from
oxidative stress, highlighting its role in maintaining cellular health. Many elements within this group are metallic and
can be toxic to living organisms at high concentrations, despite their biological usefulness.
Halogens (Group VIIA) Characteristics
Halogens are highly reactive nonmetals with seven valence electrons, seeking to complete their octets by
gaining an additional electron.
Their physical states vary under standard conditions: gaseous (Fluorine and Chlorine), liquid (Bromine), and
solid (Iodine).
Conclusion on Elemental Toxicity
It is critical to recognize that while many elements have beneficial roles in biology, they can become toxic or
damaging at elevated concentrations.
Points of Transition Metals
1. General Characteristics:
Transition metals are located in Groups IB to VIIIB (Groups 3 to 12) of the periodic table.
They are classified as metals with distinct physical and chemical properties.
2. Electron Properties:
Low electron affinities, low ionization energies, and low electronegativities characterize these elements.
The presence of loosely held electrons contributes to their metallic properties.
3. Physical Properties:
Transition metals are known for their hardness and high melting and boiling points.
They exhibit malleability, allowing them to be shaped without breaking.
