Additional Science - Chemistry

Additional Science - Chemistry

1. Atomic structure and the periodic table

   • Atoms and the periodic table
     • Dmitri Mendeleev
       • published the periodic table
       • arranged the elements known at the time in order of relative atomic mass
     • Alkali metals (group 1) Halogens (group 7) Noble gases (group 0) Transition metals Metals and non-metals
     • The atomic number (also called the proton number) is the number of protons in an atom.
       • The mass number (also called the nucleon number) is the total number of protons and neutrons in an atom.
     • Proton: charge = +1 mass = 1 Neutron: charge = 0 mass = 1
       • Electron: charge: -1 mass: 0.0005 (almost zero)
     • Most elements exist in a number of different forms or varieties called isotopes. Isotopes have the same number of protons but different numbers of neutrons, which gives them a different total mass.