Atomic Structure Guidelines | Chemistry 11th Class | MDCAT | NEET | Lets Crack MDCAT скачать в хорошем качестве

Atomic Structure Guidelines | Chemistry 11th Class | MDCAT | NEET | Lets Crack MDCAT

Atomic Structure Guidelines | Chemistry 11th Class | MDCAT | NEET | Lets Crack MDCAT Atomic structure refers to the structure of an atom comprising a nucleus (centre) in which the protons (positively charged) and neutrons (neutral) are present. The negatively charged particles called electrons revolve around the centre of the nucleus. The history of atomic structure and quantum mechanics dates back to the times of Democritus, the man who first proposed that matter is composed of atoms. The study about the structure of an atom gives a great insight into the entire class of chemical reactions, bonds and their physical properties. The first scientific theory of atomic structure was proposed by John Dalton in the 1800s. Table of Content What is Atomic Structure? Atomic Models Dalton’s Atomic Theory Thomson Atomic Model Rutherford Atomic Theory Subatomic Particles Atomic Structure of Isotopes Bohr’s Atomic Theory Dual Nature of Matter FAQs The advances in atomic structure and quantum mechanics have led to the discovery of other fundamental particles. The discovery of subatomic particles has been the base for many other discoveries and inventions. What is Atomic Structure? The atomic structure of an element refers to the constitution of its nucleus and the arrangement of the electrons around it. Primarily, the atomic structure of matter is made up of protons, electrons and neutrons. The protons and neutrons make up the nucleus of the atom, which is surrounded by the electrons belonging to the atom. The atomic number of an element describes the total number of protons in its nucleus. Neutral atoms have equal numbers of protons and electrons. However, atoms may gain or lose electrons in order to increase their stability and the resulting charged entity is called an ion. Atoms of different elements have different atomic structures because they contain different numbers of protons and electrons. This is the reason for the unique characteristics of different elements. Atomic Models In the 18th and 19th centuries, many scientists attempted to explain the structure of the atom with the help of atomic models. Each of these models had their own merits and demerits and were pivotal to the development of the modern atomic model. The most notable contributions to the field were by the scientists such as John Dalton, J.J. Thomson, Ernest Rutherford and Niels Bohr. Their ideas on the structure of the atom are discussed in this subsection. Dalton’s Atomic Theory The English chemist John Dalton suggested that all matter is made up of atoms, which were indivisible and indestructible. He also stated that all the atoms of an element were exactly the same, but the atoms of different elements differ in size and mass. Chemical reactions, according to Dalton’s atomic theory, involve a rearrangement of atoms to form products. According to the postulates proposed by Dalton, the atomic structure comprised atoms, the smallest particle responsible for the chemical reactions to occur. The following are the postulates of his theory: Every matter is made up of atoms. Atoms are indivisible. Specific elements have only one type of atoms in them. Each atom has its own constant mass that varies from element to element. Atoms undergo rearrangement during a chemical reaction. Atoms can neither be created nor be destroyed but can be transformed from one form to another. Dalton’s atomic theory successfully explained the Laws of chemical reactions, namely, the Law of conservation of mass, Law of constant properties, Law of multiple proportions and Law of reciprocal proportions. Demerits of Dalton’s Atomic Theory The theory was unable to explain the existence of isotopes. Nothing about the structure of atom was appropriately explained. Later, the scientists discovered particles inside the atom that proved, the atoms are divisible. The discovery of particles inside atoms led to a better understanding of chemical species, these particles inside the atoms are called subatomic particles. The discovery of various subatomic particles is as follows: Thomson Atomic Model The English chemist Sir Joseph John Thomson put forth his model describing the atomic structure in the early 1900s. He was later awarded the Nobel prize for the discovery of “electrons”. His work is based on an experiment called cathode ray experiment. The construction of working of the experiment is as follows: Cathode Ray Experiment It has a tube made of glass which has two openings, one for the vacuum pump and the other for the inlet through which a gas is pumped in.