Inorganic Compounds and Main Group Elements

Representative Inorganic Compounds

• Representative elements, often called main group elements, are those found in groups 1, 2, and 13-18 of the periodic table.
• Their chemistry is characterized by the formation of ions with common oxidation states.
• These compounds often exhibit diverse bonding types, including ionic bonding, covalent bonding and metallic bonding.

Group 1 (Alkali Metals)

• These elements readily lose one electron to form +1 cations (e.g., Na+, K+).
• They typically react vigorously with water to produce hydrogen gas and hydroxide ions.
• They form ionic compounds with nonmetals, exhibiting high reactivity.
• They are soft, silvery-white metals.

Group 2 (Alkaline Earth Metals)

• These elements readily lose two electrons to form +2 cations (e.g., Mg2+, Ca2+).
• They are less reactive than alkali metals but still react with water.
• They form ionic compounds with nonmetals, particularly halides.
• They are harder and have higher melting points than alkali metals.

Group 13 (Boron Group)

• Elements in this group exhibit a variable oxidation state, often +3 (e.g., Al3+, Ga3+).
• Boron (B) is a metalloid, while the others are metals.
• They are known for forming covalent compounds, particularly hydrides and halides.
• Aluminum (Al) is extremely important due to its abundance and use in various applications

Group 14 (Carbon Group)

• Elements of this group display a wide range of bonding types, including covalent, metallic, and ionic.
• Carbon (C) forms an extraordinary diversity of organic and inorganic compounds.
• The Group 14 elements show a range of oxidation states, with +4 being common.

Group 15 (Nitrogen Group)

• These elements exhibit various oxidation states, ranging from -3 to +5.
• The chemistry of nitrogen is largely dominated by covalent bonding.
• They are essential elements in biological systems, particularly nitrogen as a component of proteins and nucleic acids.

Group 16 (Oxygen Group)

• These elements exhibit a wide range of oxidation states, primarily from -2 to +6.
• Oxygen (O) is vital for life and forms oxides with most elements.
• Sulphur (S) is important industrially, forming numerous compounds.

Group 17 (Halogens)

• Halogens are highly reactive nonmetals that readily gain one electron to form -1 anions (e.g., Cl-, Br-).
• They exist as diatomic molecules and are good oxidizing agents.
• They form ionic compounds with metals and covalent compounds with other nonmetals.

Group 18 (Noble Gases)

• These elements are generally unreactive due to their stable electron configurations.
• They exhibit very limited chemical reactivity.
• They form compounds (albeit rarely) under specific conditions.

General Trends in Representative Elements

• Reactivity generally decreases across a period from left to right, and increases down a group.
• Metallic character increases down a group and decreases across a period.
• Oxidation states are often related to the number of valence electrons in the element.
• Bonding properties like ionic and covalent are often determined by electronegativity differences between the elements involved.