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Understanding chemical bonds is crucial for distinguishing compounds from mixtures. Chemical bonds involve the attraction between the atoms of chemical elements that allows the formation of chemical substances. At the most fundamental level, these bonds arise from the electrostatic forces between the positively charged nuclei of atoms and the negatively charged electrons.

Atoms can establish bonds in several ways, often by sharing or transferring electrons. The two main types of chemical bonds are ionic bonds, where electrons are transferred from one atom to another, and covalent bonds, where electrons are shared between atoms. When these bonds form, the resulting substance is known as a chemical compound. This process alters the original properties of the elements involved, creating a substance with a unique set of characteristics.

For example, when sodium (Na), a highly reactive metal, comes into contact with chlorine (Cl), a poisonous gas, they form an ionic bond to create sodium chloride (NaCl) – which is common table salt. Despite its components, table salt possesses neither the explosiveness of pure sodium nor the toxicity of chlorine gas. It’s a stable compound with its own distinct properties.

Chemical elements are the simplest forms of matter that cannot be broken down into simpler substances by chemical means. Each element is defined by the number of protons in its nucleus, which is known as the atomic number. Elements are the building blocks for all types of matter, both compounds, and mixtures.

In the context of understanding compounds and mixtures, it's important to recognize that while elements can combine to form compounds through chemical bonds, they can also be part of mixtures without such bonds. Elements maintain their identity and properties in a mixture. The periodic table of elements catalogues all recognized elements, ranging from hydrogen, with one proton, to the newly synthesized and heavy elements at the bottom of the table.

For instance, oxygen (O) and nitrogen (N), as elements, make up about 99% of the Earth's atmosphere as a mixture of gases, not chemically bonded to one another. These gases are free to move independently and can be separated through physical means such as liquefaction and fractional distillation.

Physical separation of mixtures is possible because the components are not chemically bonded and retain their individual properties. This means that physical, rather than chemical, processes can be used to separate them. There are a variety of methods for separating mixtures, depending on their physical properties such as size, state of matter, solubility, and magnetic properties.

For example, filtration can be used for a mixture of solid and liquid, where the solid is separated by trapping it using a filter medium while the liquid passes through. Evaporation is another method, which involves heating a liquid mixture to separate a dissolved solid by turning the liquid into vapor, leaving the solid behind.

Magnetic separation takes advantage of magnetic properties; a magnet can draw out magnetic materials from a mixture, leaving non-magnetic components behind. Additionally, techniques like distillation separate components based on different boiling points. Understanding these methods is essential in fields such as chemistry, environmental science, and engineering where the purity of materials is critical.