Final answer:
Atoms are the basic units and building blocks of all matter. They combine in different ways to form molecules, ranging from simple molecules like water to complex ones like DNA. Understanding atomic and molecular structures helps explain many phenomena.
Step-by-step explanation:
Atoms are the smallest unit of elements and a substructure of all things around us, whether that is the air we breathe or natural phenomena. They are the building blocks of molecules, which can be found in all matter in the universe, including air, soil, water, rocks, and living cells. Atoms have a specific atomic structure and properties that help explain many phenomena.
The first direct observation of atoms was by studying Brownian motion which provided accurate sizes for atoms. Over time, our understanding of atomic theory has evolved. One of the most significant models is the Bohr model of the atom.
When atoms combine in various ways they form molecules. These can range from simple molecules like water (H2O), where two hydrogen atoms bond with an oxygen atom, to amazingly complex molecules like Deoxyribonucleic Acid (DNA), which carries genetic instructions for the development, functioning, growth, and reproduction of all known organisms and many viruses.
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