atomic models

• Democritus Matter could not be divided into smaller pieces infinitely
• Matter is classified into physical classification (based on physical properties like state and density) and chemical classification (based on chemical composition like pure substances or mixtures)

  
• A pure substance is made up of only one type of atom or molecule, while a mixture is made up of two or more different types of atoms or molecules

  
• Mixtures can be homogeneous (evenly distributed components) or heterogeneous (components not evenly distributed)

  
• Pure substances can be classified as elements (made of one type of atom) or compounds (made of two or more types of atoms)

  
• Elements can be further classified into atoms or molecules, while compounds can be further classified into molecules or ions

  
• Types of solutions:

  • Homogeneous solution
  • Heterogeneous solution
  • Saturated solution
  • Super saturated solution

  
• Democritus proposed that matter could not be divided infinitely and introduced the concept of atoms, from the Greek word "atomos" meaning indivisible

  
• John Dalton proposed the Atomic Theory, stating that all matter is composed of tiny, indivisible particles called atoms

  
• Joseph John Thomson discovered the negative charge particles and the positive charge particles, proposing the Plum Pudding Model of the atom

  
• Thomson's model suggested that atoms are made up of even smaller particles

  
• Ernest Rutherford's Atomic Model described the atom as a tiny, dense, positively charged core called a nucleus, surrounded by lighter negatively charged electrons

  
• Neils Bohr's Atomic Model likened the atom to a solar system, with the nucleus as the sun and electrons as planets on different orbits

  
• Erwin Schrödinger proposed the Quantum Mechanical Model, stating that the atom is composed of a small positively charged nucleus surrounded by a large region with enough electrons to make the atom neutral

  
• Sub-atomic particles:

  • Proton: inside the nucleus, 1 a.m.u, positive charge
  • Neutron: inside the nucleus, 1 a.m.u, no charge
  • Electron: outside the nucleus, 1/1836 a.m.u, negative charge
• Atomic number is the number of protons in an atom, while atomic mass is the mass of an atom expressed in atomic mass units