CBSE Class 11 Chemistry Notes Chapter 2 Structure of Atom

The discovery of the proton, one of the fundamental particles of an atom, is credited to Ernest Rutherford, a New Zealand-born physicist. In 1919, Rutherford conducted experiments involving the bombardment of nitrogen gas with alpha particles, which are positively charged particles emitted by radioactive materials. During these experiments, Rutherford observed that when alpha particles collided with nitrogen atoms, they were deflected at various angles, indicating the presence of a positively charged particle within the nucleus of the atom. Based on these observations, Rutherford proposed the existence of a positively charged particle within the nucleus of the atom, which he named the "proton." He suggested that the positive charge of the proton balanced the negative charge of the electron, resulting in a neutral atom overall. Rutherford's discovery of the proton revolutionized the understanding of atomic structure and paved the way for further advancements in the field of nuclear physics.

Neutron discovery

The discovery of the neutron, another fundamental particle of an atom, is credited to James Chadwick, an English physicist. In 1932, Chadwick conducted experiments involving the bombardment of beryllium atoms with alpha particles. During these experiments, Chadwick observed the emission of a previously unknown type of radiation that had no electric charge and could penetrate materials more effectively than other types of radiation. Chadwick hypothesized that this radiation consisted of neutral particles with a mass similar to that of a proton. He conducted further experiments to confirm his hypothesis, including measurements of the scattering of these neutral particles by various materials. These experiments provided conclusive evidence for the existence of the neutron. Chadwick's discovery of the neutron was a significant milestone in the field of nuclear physics. It provided crucial insights into the structure of atomic nuclei and paved the way for advancements in nuclear science, including the development of nuclear reactors and nuclear weapons.

Isotopes, Isobars, isotones and Isoelectronic

Isotopes, isobars, isotones, and isoelectronic species are terms used in nuclear and atomic physics to describe different properties of atoms and their nuclei.

Isotopes: Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons in their nuclei. This results in variations in their atomic mass. For example, carbon-12, carbon-13, and carbon-14 are isotopes of carbon.

Isobars: Isobars are atoms of different elements that have the same mass number, meaning they have the same total number of protons and neutrons in their nuclei, but different atomic numbers (number of protons). For example, carbon-14 and nitrogen-14 are isobars because they both have a mass number of 14.

Isotones: Isotones are atoms of different elements that have the same number of neutrons but different numbers of protons in their nuclei. This results in variations in their atomic mass and atomic number. For example, carbon-14 and nitrogen-15 are isotones because they both have seven neutrons in their nuclei.

Isoelectronic species: Isoelectronic species are atoms, ions, or molecules that have the same number of electrons. This means they have identical electron configurations. Isoelectronic species may belong to different elements and may be either atoms or ions. For example, the fluoride ion (F^-), the neon atom (Ne), and the sodium ion (Na^+) are isoelectronic because they all have ten electrons.

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