The fundamental unit of matter, consisting of a nucleus containing protons and neutrons, surrounded by electrons in energy levels, representing a specific chemical element.
An atom is composed of two main parts:
The central core of the atom containing protons (positively charged particles) and neutrons (uncharged particles), concentrated mass, and responsible for the atom’s identity.
The region surrounding the nucleus where electrons (negatively charged particles) orbit in energy levels, determining the atom’s reactivity and interactions.
The central core of an atom, composed of positively charged protons and neutrally charged neutrons, housing most of the atom’s mass and determining its chemical properties.
The Geiger-Marsden alpha scattering experiment, also known as the gold foil experiment, was conducted in 1909 by Hans Geiger and Ernest Marsden under the guidance of Ernest Rutherford. The experiment played a crucial role in shaping our understanding of the structure of the atom.
In the experiment, a thin sheet of gold foil was placed in the path of a beam of alpha particles, which are positively charged particles emitted by a radioactive source. The alpha particles were directed towards the gold foil, and a circular detector screen surrounded the foil.
Based on the prevailing model of the atom at the time, which was J.J. Thomson’s “plum pudding” model, it was expected that the alpha particles would pass through the gold foil with minimal deflection. According to this model, atoms were thought to be composed of a diffuse cloud of positive charge with embedded negatively charged electrons.
However, the experiment yielded surprising results. While most alpha particles passed through the foil as expected, some of them experienced significant deflection, and a small fraction even bounced back in the direction from which they came. This observation was highly unexpected and defied the predictions of the plum pudding model.
The Geiger-Marsden experiment revolutionized our understanding of atomic structure, leading to the modern concept of the atom with a nucleus containing protons and neutrons, and electron orbits around it. This model forms the foundation of nuclear physics and atomic theory today.
An atom is composed of subatomic particles:
Positively charged particles found in the nucleus, contributing to the atom’s mass and identity. Each proton has a charge of +1.
Neutrally charged particles located in the nucleus alongside protons. They add mass to the nucleus without affecting the atom’s charge.
Negatively charged particles orbiting the nucleus in energy levels or electron shells. They contribute to the atom’s size and reactivity. Each electron has a charge of -1.
The nucleus, containing protons and neutrons, forms the atom’s central core, while the electron cloud surrounds it. The number of protons determines the element’s identity (atomic number), while the sum of protons and neutrons gives the atomic mass.
Nuclear physics is the study of the properties, behavior, and interactions of atomic nuclei and their constituent particles, like protons and neutrons, exploring the fundamental forces that govern the nucleus.
