Atomic Theory and Subatomic Particles

Atomic Theory

• Atoms are the smallest unit of matter.
• Everything is made up of atoms.

Atomic Model Evolution

• Dalton's Atomic Theory (1803) described atoms as solid spheres, like billiard balls.
• Thomson's Plum Pudding Model (1904) proposed a sphere of positive charge with electrons embedded within.
• Rutherford's Nuclear Model (1911) discovered the nucleus, a dense, positively charged center of the atom.
• The Cathode Ray Tube Experiment led to the discovery of electrons.
• Robert Millikan's Oil Drop Experiment measured the charge and mass of an electron.
• Eugene Goldstein discovered protons.
• Chadwick discovered neutrons.
• Niels Bohr's Planetary Model depicted electrons orbiting the nucleus in specific energy levels.
• Erwin Schrӧdinger's Quantum Theory proposed the orbital model, with electrons existing in probability clouds.

Subatomic Particles

• Protons are located inside the nucleus and determine the atom's atomic number.
• Electrons are located in a cloud surrounding the nucleus and contribute to the atom's overall charge.
• Neutrons are located inside the nucleus and have a mass similar to protons.

Important Concepts

• Anions are negatively charged ions.
• Cations are positively charged ions.
• The mole is a unit of measurement used in chemistry to represent the amount of a substance.
• Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons.
• Atomic mass number is a rounded estimate of the combined number of protons and neutrons in an atom.