ATOMIC STRUCTURE || DISCOVERY OF Elecron,Proton and Neutron скачать в хорошем качестве

ATOMIC STRUCTURE || DISCOVERY OF Elecron,Proton and Neutron

Atomic structure explains how an atom is built and how its particles are arranged. An atom is the smallest unit of matter that retains the properties of an element. What is an Atom? An atom consists of two main parts: Nucleus (center) Extra-nuclear region (space around nucleus) Subatomic Particles Protons (p⁺) Found in the nucleus Positive charge Mass ≈ 1 amu Number of protons = Atomic number (Z) Neutrons (n⁰) Found in the nucleus No charge Mass ≈ 1 amu Protons + Neutrons = Mass number (A) Electrons (e⁻) Revolve around the nucleus Negative charge Very small mass Responsible for chemical properties Electron Distribution (Bohr’s Model) Electrons move in fixed energy levels called shells or orbits: K, L, M, N … (n = 1, 2, 3, 4 …) Maximum electrons in a shell = 2n² Example: K shell → 2 electrons L shell → 8 electrons Modern Atomic Model (Quantum Mechanical Model) Electrons do not move in fixed paths They are found in regions of probability called orbitals Orbitals are of different shapes: s, p, d, f Key Points to Remember Atom is electrically neutral Most of the mass is concentrated in the nucleus Chemical reactions involve electrons, not nucleus