What are molecules? A molecule is a group of two or more atoms held together by chemical bonds. It is the smallest particle of a substance that retains all the chemical and physical properties of that substance. In this simple example, we have two atoms connected by a chemical bond, forming a basic molecule.
Molecules can be classified into different types. Same element molecules consist of atoms of the same element, like oxygen gas, which has two oxygen atoms bonded together. Compound molecules, on the other hand, are made up of atoms of different elements. Water is a perfect example, with one oxygen atom bonded to two hydrogen atoms. These different types of molecules have distinct properties and behaviors based on their composition.
Chemical bonds are the forces that hold atoms together in molecules. There are two main types of chemical bonds. Covalent bonds occur when atoms share electrons, as seen in the hydrogen molecule where two hydrogen atoms share a pair of electrons. These bonds are common in gases and organic compounds. Ionic bonds, on the other hand, form when electrons are transferred from one atom to another, creating oppositely charged ions that attract each other. Sodium chloride, or table salt, is a classic example where sodium donates an electron to chlorine, forming a strong ionic bond between the positively charged sodium ion and the negatively charged chloride ion.
The shape of a molecule is crucial as it determines many of its properties. Molecular shapes are influenced by the arrangement of atoms and the repulsion between electron pairs. For example, water has a bent shape with an angle of 104.5 degrees between the hydrogen atoms. This bent shape gives water its unique properties, including its ability to dissolve many substances. Methane, on the other hand, has a tetrahedral shape with the carbon atom at the center and four hydrogen atoms arranged symmetrically around it. These different molecular shapes directly affect physical properties, chemical reactivity, biological function, and material characteristics of substances.
To summarize what we've learned about molecules: A molecule is a group of two or more atoms held together by chemical bonds. Molecules can be made of the same element, like oxygen gas, or different elements, like water and carbon dioxide. The type of chemical bond, whether covalent or ionic, determines how atoms are held together in molecules. The shape of a molecule is crucial as it determines its physical properties, chemical reactivity, and biological function. Understanding molecules is fundamental to many scientific fields including chemistry, biology, medicine, and materials science. This knowledge helps us develop new medicines, materials, and technologies that improve our daily lives.