What are atoms, if everything is composed of elements?

               Philosophers in ancient times believed that everything in the universe was composed of extremely small and indivisible units called atoms. But their idea of an atom differed from what modern scientists understand of it today. In fact, elements, the basic building blocks of matter, are composed of tiny particles called atoms.

               And what are atoms made up of, in turn? Every atom has a nucleus. It is made up of protons and neutrons and is surrounded by the electron cloud.

               Protons possess positive electrical charge and electrons carry negative electrical charge. Neutrons have no electrical charge at all. An atom is usually neutral, as the number of protons and electrons in it is equal. John Dalton, a renowned English scientist, is known for introducing atomic theory into chemistry.

               Atoms of the same element are identical. For example, all atoms in oxygen are the same. Atoms of one element can combine with atoms of another element to form new substances. Such new substances are known as chemical compounds. A compound is atoms from diverse elements combined together. Water, sugar and salt are examples.

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