Atoms, molecule and ions

• Structure of the atom in terms of protons, neutrons and electrons

  an atom has a nucleus made up of protons and neutrons, with electrons orbiting around the nucleus. Protons have a positive charge, neutrons have no charge, and electrons have a negative charge.
• Dalton's Atomic Theory (1803)


  • Atoms were tiny, indivisible particles that made up all matter
  • Each element is made of atoms with a unique mass
  • Electrons orbit the nucleus at specific distances, and each orbit corresponds to a specific energy level
• Dalton's Atomic Theory proposed


  Early 19th Century
• Discovery of Electrons


  J.J. Thomson discovered electrons through his experiments with cathode rays, suggesting that atoms were not indivisible as Dalton proposed
• Discovery of Electrons

  Late 19th Century
• Rutherford's Nuclear Model (1911)


  Atoms have a dense, positively charged nucleus surrounded by negatively charged electrons
• Rutherford's Nuclear Model proposed

  Early 20th Century
• Bohr's Model of the Atom (1913)


  Niels Bohr expanded on Rutherford's model by introducing the idea of quantised electron orbits or energy levels
• Relationship between charges on ions and group in periodic table Group number 


  The group number indicates the number of valence electrons an element has. Elements in the same group typically have similar chemical properties because they have the same number of valence electrons.
• Relationship between charges on ions and group in periodic table Valence Electrons

  Valence electrons are the outermost electrons in an atom, involved in chemical bonding. The number of valence electrons determines the charge an atom will attain when it forms an ion.
• Relationship between charges on ions and group in periodic table Ion Charge


  Atoms gain or lose electrons to achieve a stable electron configuration, typically the configuration of the nearest noble gas. When atoms gain electrons, they become negatively charged ions, and when they lose electrons, they become positively charged ions.
• Relationship between charges on ions and group in periodic table Group 1 


  Elements in Group 1 tend to lose one electron to form ions with a 1+ charge
• Relationship between charges on ions and group in periodic table Group 2

  Elements in Group 2 tend to lose two electrons to form ions with a 2+ charge
• Relationship between charges on ions and group in periodic table Group 3

  Elements in Group 3 can lose three electrons to form ions with a 3+ charge 
• Relationship between charges on ions and group in periodic table Group 5 


  Elements in Group 5 can gain three electrons to form ions with a 3- charge
• Elements in Group 6

  Can gain two electrons to form ions with a 2- charge
• Elements in Group 7

  Can gain one electron to form ions with a 1- charge
• Noble gases in Group 8


  Typically do not form ions under normal conditions because they have stable electron configurations
• Atomic number 


  The atomic number is the number of protons in an atom's nucleus.
• Mass number 


  The mass number of an atom is the total number of protons and neutrons in its nucleus. It is often represented by the symbol "A."
• Isotopes are atoms that contain the same number of protons but different numbers of neutrons.
• Ionic bonding occurs when metals lose electrons to nonmetals to form positive ions and negative ions respectively.