Key Types of Chemical Compounds and Their Characteristics
A chemical compound is a chemical substance that has molecules with two or more elements. Matter consists of atoms of various elements. Elements either exist as pure forms or in a combined form. The combined form is known as a chemical compound. A pure element is made up of atoms that are found in that element. Each element gets its characteristic properties due to the characteristic nature of the atoms that comprise that element. For instance, atoms of iron are very different from atoms of gold. Each atom has its symbol which is often an abbreviation of its name or its name in Latin.
Chemistry involves studying how atoms of various elements combine to form compounds. Ethanol for instance is formed from the elements carbon, hydrogen, and oxygen. It contains specific ethanol molecules. The chemical formula of ethanol C2H5OH indicates the types and the numbers of atoms that are present in the compound. Water which has a chemical formula H2O consists of 2 atoms of hydrogen and one atom of oxygen. Salt or sodium chloride is a compound that has sodium and chlorine in an equal ratio. It has sodium ions that are positively charged and chlorine ions that are negatively charged.
From these examples, we can get a basic classification of compounds- covalent or molecular compounds and ionic compounds, compounds that comprise molecules are called molecular compounds, and compounds that comprise ions are called ionic compounds.
Classification of Pure Substance
Matter can be categorized into various categories. In chemistry, the category that we begin from is that of pure substance and mixtures. A pure substance is a chemical material that has a consistent composition throughout. All parts of a pure substance will have the same chemical properties regardless of where it is obtained. Pure substances are further classified as elements and compounds. Elements are chemicals that cannot be broken down into smaller units. While substances that can be broken down into their constituent units are called compounds.
Classification of Metal Carbonyls
Metal carbonyls are a class of organometallic compounds. They are of two types: mononuclear carbonyls that have one metal atom per molecule and polynuclear carbonyls that have two or more metal atoms per molecule.
Classification of Alkyl Halides
Alkyl halides or haloalkanes are compounds in which hydrogen atoms in an alkane are replaced by atoms from the halogen family such as chlorine, fluorine, etc. Haloalkanes are of 3 types primary, secondary and tertiary. In primary haloalkanes, the carbon connected to the halogen on one end is attached to a single alkyl group on the other end. In secondary, the carbon connected to the halogen is connected to two same or different alkyl groups. In tertiary alkyl halides, the carbon atom is connected to three same or different alkyl groups.
Classification of Carboxylic Acid
Carboxylic acids are those organic compounds in which the carbon atom is connected to the oxygen atom by a double bond and a hydroxyl group by a single bond. Carboxylic acids are categorized as aromatic, unsaturated, and saturated aliphatic, amino acids, keto and hydroxy acids, and polycarboxylic acid.
Classification of Organic Compounds
[Image will be Uploaded Soon]
Open Chain Compounds: Also called acyclic or aliphatic organic compounds, they consist of chains that may be straight or branched.
Closed Chain Compounds: Also called alicyclic or ring organic compounds, they consist of atoms of carbon that are joined to each other in a ring structure. If the chain also contains atoms that are not carbon then the ring is heterocyclic.
Aromatic Compounds: Aromatic compounds are organic compounds with a unique set of properties. They also gave a ring structure. They can also have more than one atom in the ring.
Classification based on the functional group: An atom or a set of atoms that are combined in a particular way to an organic compound is called a functional group. These groups impart specific chemical properties to the compounds they are joined to. Some examples of functional groups are: -OH,-COOH et al.
Homologous Series: A series of organic compounds where each part has the same functional group that imparts its special characteristics. For instance: alkanes, haloalkanes, amines, etc.
Fun Fact
An organic compound was first synthesized from inorganic substances by the German chemist Friedrich Wöhler in 1828. This discovery was accidental. He synthesized urea by mixing the salts silver cyanate and ammonium chloride. From this result, he proposed that atoms used different methods of arranging themselves into molecules and that the characteristics of these molecules are based on the molecular structure. Other chemists followed suit and by the 1860s, the notion that some magical “vital force” was required for the formation of organic compounds was debunked.
FAQs on Classification of Chemical Compounds: A Complete Guide
1. What are the main ways to classify chemical compounds?
Chemical compounds are primarily classified in two main ways. The first is based on their chemical composition, dividing them into organic compounds (containing carbon-hydrogen bonds) and inorganic compounds (all other compounds). The second method is based on the type of chemical bonds they contain, such as ionic, covalent, or metallic bonds.
2. How are organic compounds broadly classified?
Organic compounds are classified based on their carbon skeleton structure. The two main categories are:
- Acyclic or Open-Chain Compounds: These compounds have a straight or branched chain of carbon atoms. Examples include ethane and isobutane.
- Cyclic or Closed-Chain Compounds: These compounds contain one or more rings of atoms in their structure. They are further divided into homocyclic (rings made only of carbon) and heterocyclic (rings containing at least one atom other than carbon).
3. What is the main difference between an organic and an inorganic compound?
The primary difference lies in the presence of carbon. Organic compounds are defined as compounds containing carbon atoms, typically bonded to hydrogen (C-H bonds). In contrast, inorganic compounds generally do not contain carbon, with a few exceptions like carbonates and cyanides. Organic compounds form the basis of life, while inorganic compounds are typically of mineral origin.
4. How are compounds classified based on their chemical bonds?
Based on the nature of their chemical bonds, compounds are classified as:
- Ionic Compounds: Formed by the transfer of electrons between a metal and a non-metal, creating ions held by electrostatic attraction (e.g., Sodium Chloride, NaCl).
- Covalent Compounds: Formed by the sharing of electrons between non-metal atoms (e.g., Water, H₂O).
- Metallic Compounds: Characterised by a 'sea' of delocalised electrons surrounding a lattice of positive metal ions (e.g., found in alloys like brass).
5. Why is the classification of chemical compounds important?
Classifying chemical compounds is crucial because it helps us to systematically study the millions of known substances. This system allows chemists to:
- Predict the physical and chemical properties of a compound based on its category.
- Understand its reactivity and how it might behave in a chemical reaction.
- Assign a unique and logical name to each compound (nomenclature).
- Organise chemical knowledge in a structured and understandable way.
6. What makes aromatic compounds like benzene different from other cyclic compounds?
Aromatic compounds, like benzene, are a special class of cyclic compounds that possess a high degree of stability. This is due to a continuous ring of overlapping p-orbitals containing a specific number of delocalised electrons (following Hückel's rule). This delocalisation of electrons makes them much less reactive and chemically distinct from non-aromatic cyclic compounds (alicyclic compounds) like cyclohexane, which behave more like open-chain compounds.
7. Are all compounds that contain carbon considered organic?
No, not all compounds containing carbon are classified as organic. There are a few key exceptions that are traditionally studied as inorganic compounds due to their properties. These include:
- Carbonates (e.g., CaCO₃)
- Carbides (e.g., SiC)
- Cyanides (e.g., KCN)
- Oxides of carbon (CO and CO₂)
These compounds lack the carbon-hydrogen bonds characteristic of most organic substances.
8. What are the basic types of inorganic compounds?
Inorganic compounds are generally classified into four main types based on their chemical properties and composition:
- Acids: Substances that produce hydrogen ions (H⁺) in water (e.g., Hydrochloric Acid, HCl).
- Bases: Substances that produce hydroxide ions (OH⁻) in water or accept protons (e.g., Sodium Hydroxide, NaOH).
- Salts: Ionic compounds formed from the reaction of an acid and a base (e.g., Potassium Nitrate, KNO₃).
- Oxides: Compounds containing at least one oxygen atom combined with another element (e.g., Iron Oxide, Fe₂O₃).
