Molecule
Definition
A molecule is defined as the fundamental units of chemical compounds formed when two or more atoms chemically bond together.
- It forms the smallest unit of the substance.
- The atoms of the molecule can be of the same element like oxygen (O2) and hydrogen (H2) (diatomic molecule), or they can be different elements, such as water (H2O) or carbon dioxide (CO2).
- Molecule retains the physical and chemical properties of that substance.
- Molecules are held together by covalent bonds or ionic bonds.
Chemical Bond
A chemical bond is a force that holds two or more atoms together in a molecule. The interactions between atoms is due to the electrostatic forces (as in ionic bonds) or the sharing of electrons (as in covalent bonds). These bonds determine the stability, properties, and behaviour of substances.
Type of Chemical Bond
There are three main types of chemical bonds:
- Covalent Bond
- Ionic Bond
- Hydrogen Bond
Covalent Bond
Covalent bonds also referred to as molecular bonds involve the equal sharing of electrons between atoms. It is common between two nonmetals. There are two main types of
covalent bonds:
- Single Covalent Bonds: In a single covalent bond, atoms share one pair of electrons. Examples include hydrogen gas (H2) and chlorine gas (Cl2).
- Multiple Covalent Bonds: In multiple covalent bonds, atoms share two or more pairs of electrons. Examples include oxygen gas (O2) and nitrogen gas (N2).
Ionic Bond
Ionic bonds form between atoms when one atom transfers one or more electrons to another atom. This transfer results in the formation of positively charged ions (cations) and negatively charged ions (anions). The oppositely charged ions are attracted to each other by electrostatic forces, forming an ionic bond. Ionic bonds are typically formed between a metal atom (which tends to lose electrons) and a nonmetal atom (which tends to gain electrons).
Examples of compounds with ionic bonds are sodium chloride (NaCl), potassium iodide (KI), and magnesium oxide (MgO).
Hydrogen Bond
It is not ionic or covalent; it’s a dipole-dipole attraction that forms between a hydrogen atom and an electronegative a tom. Important in biological molecules like DNA and proteins.
Isomer
Isomers are those molecules which have same molecular formula but different arrangements of atoms. Isomers can exhibit different physical and chemical properties due to their distinct structures.
There are several types of isomerism, including structural isomerism, geometric isomerism, and optical isomerism.
